The energy meters will then sample at close to its maximum frequency. For instance measuring 10 KHz with a PD10 Sensor and Nova II where the maximum frequency for every pulse on the Nova II is 4 KHz: in this case, the Nova II will pick out pulses at a rate of close to 4 KHz and sample them, i.e. the Nova II will record 40% of the pulses.
This can sometimes happen when the battery of the Power and Energy Meters
is completely discharged and then the charger is plugged
in. The Power and Energy Meters is powered up but the contrast voltage on
the LCD is not functioning, so it looks as though it is
off; and usually the backlight switches on and off normally.
The solution is to first switch OFF the Power and Energy Meters properly
by pressing the On/Off button for 4-5 seconds, and then
switching it back ON by momentarily pressing the On/Off
button, as normal.
The Power and Energy Meters will also fail to operate if you attempted to download
a software upgrade and there was a malfunction in the download,
see the question "Can I upgrade " below.
the field-upgrade process fails (example, unplug of
the USB cable during the upgrade), the Power and Energy Meters will
not function properly. Therefore, when turning on
the Power and Energy Meters the user gets a blank screen. Note: The
Power and Energy Meters can still communicate with the PC. Try to
reinstall the Power and Energy Meters software as described above.
Think of it like a voltmeter or ammeter, these have to be recertified/recalibrated as well like most other pieces of test equipment. In general, our instruments are unlikely to drift or fail over time like a sensor might that is constantly exposed to laser energy. But the possibility exists. So the general practice in our industry is to have Power and Energy Meterss recalibrated and recertified as well. ISO standards and FDA, as well as other agencies, require both be recalibrated and recertified.
Clearly there are many possible power/energy distributions, and laser damage to a sensor can occur at a local peak power density spot even if the overall
power density is within spec. Ideally, then, a damage threshold spec should depend on what the beam profile is. However, it is very difficult to calculate what
the peak power density will be at the center of a beam unless it is a uniform ("top hat") beam - which is seldom the case. Further complicating things is the
fact that a laser spot's borders are not solid lines but rather have a certain "fuzziness", which is why modern beam profiling equipment offers a variety of
mathematical definitions of beam size when measuring a profile.
In order to provide users with a useable, practical guideline, we do define our specs in terms of a uniform distribution. However, when we determine the actual
damage thresholds for our sensors, we take a level of safety margin into account, so that for "typical" beams whose profile is not too complex our spec will
roughly reflect the peak power density of the beam. As a further safety measure, we also always recommend that users choose a sensor that, all other things
being equal, will work at not more than 50% of the specified damage threshold.
If you need to change the sensor on a meter for additional measurements, you do need to power the meter Off and On again in order to refresh the meter with the new sensor information.
However, the latest firmware for the Nova II and Vega (v2.06) includes the ability to automatically read a different sensor information, when it is connected, without the requirement to power the meter Off an On again.
The latest firmware for the Nova II and Vega is available at;
In all Ophir instruments, all adjustments, including zeroing internal circuits, are done from the software. This ensures simple and accurate realignment. The zeroing process helps eliminate internal biases in the unit which could affect accuracy of measurements. It is recommended to re-zero the instrument every 2 months for best performance. Specific instructions for doing this are found in the relevant User Manual for each instrument.
If the power is P and the diameter of the beam is D then
the power density is P /(.785 * D2) . If it is a pulsed
laser and the energy is E, the repetition rate is R and
the diameter is D then the power density is E*R/(.785 *
D2), The energy density is E/(.785 * D2)
If the calibrated wavelength is W1 and I want to measure
at wavelength W2 then I look at the relative sensitivities
on the curve at W1 and W2 and calculate as follows: Sensitivity
at W1: s1 Sensitivity at W2: s2 When instrument is set to
W1 and I measure W2, then multiply reading at W2 by s1/s2
to get correct reading at W2.
A: With normal usage we recommend calibrating every 12 months. To accommodate shelf time and shipping time new manufactured product comes with a calibration sticker that shows a recalibration period of 18 months from manufacturing. However this does not negate the recommended 12 month recalibration interval should you receive the product with more than 12 months remaining on the new manufactured calibration sticker.
A: All Ophir power meters, including photodiode power meters, have an air gap between the fiber tip and the sensor. Therefore they measure the power emitted by the fiber into the air and do not take into account any reflection losses there are in the fiber. Therefore, if in actual use, the fiber will be coupled with no loss to another element, then the losses should be added to the reading. These losses are usually about 4%. Thus if the reading on the Ophir meter is say 100mW, then in lossless use, the real power will be 104mW.
A: All lasers or optical delivery systems degrade over time. A Power and Energy meter will help verify this and quantify this over time. It's a diagnostic tool to ensure that the laser system is delivering the specified amount of energy or power. The precise measurement of energy may critical in many of the processes in which they employed.
A: They start looking for causes, like lenses degraded, output couplers degraded, bad fiber, bad power supply. Many call their customer service party, whether it' s the laser company or and independent field service org.
A: Most are aware that they have to measure power/energy and many lasers come with internal monitoring systems. Most do not come with external meters. Since there is usually a discrepancy between what the internal meter measures and what is actually coming out, there is often a need to measure externally as well as internally. However, many users do not realize this.
A: Yes, many users of aesthetic lasers may not have that awareness that what actually comes out of the laser delivery system may vary dramatically from what the internal monitors displays what is coming out and needs external monitoring.
A: This depends on whether you are using a thermopile sensor head or a photodiode sensor head. With our most sensitive thermopile sensor head, model 3A-FS one can measure down to 20 uW. With our photodiode sensor heads we have a several types, silicon, InGaAs and Germanium. Each has a spec on minimum power, which can be in the nW or even pW range.
A: For pyroelectric energy sensor heads there is no limit on how short the pulse is, as they are integrating devices. As long as one does not exceed the damage threshold expressed in terms of energy density then they will accurately integrate pulses as short as femtoseconds. With thermopile sensors they similarly can be used as integrating devices to measure energy, although one can only measure single pulses every few seconds as they have a much slower response time than pyroelectics. With repetitive short pulses one can measure the average power with a thermopile with no restriction on how short the pulses are, as long as the energy density damage threshold is not exceeded. The spec for damage threshold varies on type of absorbing surface of each sensor head type. Consult our damage threshold charts or use the Sensor Finder for detailed information.
A: The problem of irradiating the head with different input powers is analogous to that of filling a tank that has a hole in the bottom. The rate equation describing the accumulating energy (heat) in the head is
where P is the power incident on the sensor, is the characteristic time constant of the heat dissipation (thermal time constant) and Q is the heat in the sensor.
The complete solution to this differential equation is an exponential of the form:
The parameters in the above equation are determined by the head characteristics and the initial conditions.
For a generic head starting at room temperature this equation becomes:
where Pcont is the maximum power permitted for continuous operation. We can use the other known operating limits of the head to solve for , the thermal time constant of the head.
Here Pint is the power permitted for intermittent use for tint seconds. With we can calculate the permitted operating time for an arbitrary power.
For your case we have the known limits:
75 W continuous
500 W for 1 min
So Pcont = 75 W. Using Pint = 500 W and tint = 60 sec gives a value of = 370 sec. Combining we have:
which tells us how long we can irradiate the sensor (from cold start) for any given incident power.
With 150 W, you could irradiate the sensor for 250 sec.
However, if you want to cycle between irradiating and cool down continuously, you don't reach ambient before the laser is turned on again. If the laser is on for t(on) and then turned off (or blocked) for t(cool), the head will cycle between two values of Q: Q(max) at the end of the heating (related to Pcont) and Q(0) at the end of the cool down and start of the heating.
Using the general solution for Q above, we can solve for the behavior during the heating and cooling phases.
This leads to the following equation relating P, t(on) and t(cool):
where Pcont and are determined as described in the first case above. Note that the behavior is essentially the same as for the previous case in which we started with the sensor at ambient but with the maximum power permitted for a given irradiation time reduced to
You indicated that you want to take 10 readings of 20 seconds each so t(on) is 200 seconds. For incident power of 150 W and measurement time of 200 sec, we need a cool down time of 470 sec. Other parameter sets can be considered as necessary.
A: Clearly there are many possible power/energy distributions, and laser damage to a sensor can occur at a local peak power density spot even if the overall power density is within spec. Ideally, then, a damage threshold spec should depend on what the beam profile is. However, it is very difficult to calculate what the peak power density will be at the center of a beam unless it is a uniform ("top hat") beam - which is seldom the case. Further complicating things is the fact that a laser spot's borders are not solid lines but rather have a certain "fuzziness", which is why modern beam profiling equipment offers a variety of mathematical definitions of beam size when measuring a profile.
In order to provide users with a useable, practical guideline, we do define our specifications in terms of a uniform distribution. However, when we determine the actual damage thresholds for our sensors, we take a level of safety margin into account, so that for "typical" beams whose profile is not too complex our specification will roughly reflect the peak power density of the beam. As a further safety measure, we also always recommend that users choose a sensor that, all other things being equal, will work at not more than 50% of the specified damage threshold.
A: The Power Accuracy of +/-3% refers to the absolute uncertainty of the measured value. For example, for a 2 Watt reading, the actual "true" value would be between 1.94 W to 2.06 W (with reference to NIST, to which all our calibration is traceable). This assumes the reading is from about 5% of full scale up to full scale. It should be noted that our accuracy specification is in general based on 2 sigma standard deviation.
Repeatability of the measurement (assuming the laser itself is perfectly stable) is limited in the best case by the power noise level of the sensor, and is typically up to the +/- 1% range depending on the thermal stability of the environment. Stability at higher powers from the middle to the top of the range of the sensor head is usually better than the low end. This is due to small temperature variations having less of an effect as they are proportionally a lower percentage of the total power.
For more information, refer to our Web tutorial at: http://www.ophiropt.com/laser-measurement-instruments/laser-power-energy-meters/tutorial/calibration-procedure
A: Yes you can for Ophir thermal sensors, but then the output will not be calibrated. Ophir sells an adapter (Ophir P/N 7Z11010) that connects to the D15 plug and has BNC output. This will make available the raw output from our thermal sensors.
A:How long you fire the laser into the meter depends on you. Some manufacturers do it 100% of the time via a beam splitter. That way they have a constant feedback system to allow them to not only monitor the power output, but also to control it so the laser is stable. Other people only do it for a short time to verify the setting is producing the correct amount of power. For different applications different sensors would be needed. For continual monitoring we would recommend a sensor that is designed to have the laser on it all the time. For short time measurements, a sensor designed for short use would be more ideal. For lasers that are pulsed, we recommend firing the laser a couple of times to get an understanding of the pulse to pulse change as well as being able to monitor the average. However, some applications only want to verify the energy setting, so they only fire the laser once to see if they are ready to go. Again, the decision is up to you. Processing the information in the PLC is completely up to you. Usually this requires some form of calibration so you can take the information you are delivering to the PLC and correlate it with your operator display. I.e. Volts/Watt. How many Volts from the sensor is equal to X amount of Watts the laser just produced.
A: The biggest issue is picking out the appropriate sensor that will measure the laser light (most will measure other types of broadband light as well). Since it is not trivial to find the best sensor for a given application, we recommend using our Sensor Finder available on our website that automatically calculates the best sensor for the measurement conditions you input. However, let us list below the main criteria:
First of all, do you want to measure average power or pulse energy? If power, then choose a thermal or photodiode sensor. If energy, then if the repetition rate is less than one pulse every 5s, then you can use a thermal or pyroelectric sensor. If faster than that, then a pyroelectric.
After you have chosen the type of sensor, then look at the dynamic range and choose a sensor that will be able to measure the highest and lowest power/energy you want to measure.
Check that the sensor covers the wavelength region you want to measure.
Now check the damage threshold. One needs to accurately know how much power or energy density one has in order to select a sensor that will not be damaged. To do that one needs to know the beam spot size, and what the energy distribution is, since for example a Gaussian beam has much higher density in the peak of the beam than a flat top or other modal beam. If the laser is pulsed, one also has to know the pulse length in time as most sensors have a different damage threshold value based on peak power; a shorter pulse with the same energy per pulse will give a much high peak power and will more readily damage the sensor. If one cannot seem to find a sensor that will not damage, then one needs to look attenuation options including beam splitters, diffusers, ND filters and possibly measuring just the leakage through a mirror.
In the above analysis there are some trade-offs.
Dynamic range that one needs to measure. Typically one can get roughly 3 ½ decades of range from a single sensor. ND filters and/ or other attenuation options can extend that by any number of decades. Of course with each attenuation option the uncertainty of the measurement increase, so the trade-off here would be dynamic range with a single sensor and extending with attenuators but having to sacrifice uncertainty, therefore accuracy. One may find that it may be better to have 2 sensors, one more sensitive and one able to measure higher power or energy.
Multiple lasers. Many end-users try to measure as many lasers as they can with as few sensors as they can in order to reduce their cost. To do this there may be some trade-offs. Maybe one won't be able to cover their full dynamic range of each laser measurement, or they have to sacrifice accuracy to cover their full range. In some cases they'll just have to get more sensors to cover all their lasers. The trade-off here is cost.
. Physical size of the sensors. Most end-users usually want the smallest physical size sensor possible, or maybe a large aperture with large sensing area, but the housing small. There may be some trade-offs there. If it's high power, there may an issue in cooling the sensor; either through convection, conduction, forced-air, or water. Each comes with its own trade-off. If attenuators are used, the space they require may be an issue.
An explanation of how we do this is given in our catalog introduction and on our website.
A recent check of our 5000W head by PTB in Germany shows excellent agreement between our calibration and their standards as enclosed here. The following is the correspondence between our sensor and their standard at powers up to 1400W (the highest available at PTB).
A: In order to get a meaningful power reading on a power meter, the signal being measured must be considerably larger than the noise.
In fact there is a measure of this, the signal to noise ratio or SNR that is often used. If the SNR is 1 then the noise is the same size as the
signal and this signal is barely distinguishable. There are some that will quote this number as the minimum measurable, but most agree
that the signal must be considerably larger than the noise to be measurable. One criterion used by many is 10:1 SNR as the minimum
useable measurement. However, when the noise referred to is 1 standard deviation or 1 Sigma, then a certain amount of the time the
noise is 2 times this or even 3 times so 10:1 SNR 1 Sigma is still not a very precise measurement. For these above reasons, Ophir has
taken a particularly strict definition of minimum measurable power and that is 20 times the 3 Sigma noise value. This is 6 times as strict
as the usual 10:1 1 Sigma value often given or implied. The Ophir value means that most of the time, the noise does not exceed more
than 2% of the signal.
A: One has to be careful about this since many vendors quote the damage threshold at a power much lower than the maximum power of
the particular sensor being advertized. As an extreme case, a meter that can measure up to 1000W, may be quoted a certain damage
threshold and in a footnote it may be noted that this damage threshold is for 10W. The damage threshold can go down dramatically with
power and the damage threshold at 1000W may be 4 or 5 times less than at very low powers. Ophir always quotes damage threshold
for a particular sensor at the highest power the sensor can measure.
A: The answer is a little more complicated, unfortunately. Yes, the Quasar has a digital link, however there are electronic components inside the Quasar that amplify and massage the signal coming from the FL500A, before it's digitized. While those components most likely will not slowly degrade or fail it's possible, hence the need to have the Quasar verified like any other piece of electronic equipment. Think of the Quasar like a Picoammeter with a digital connector output. They need to be regularly verified, and if necessary, recalibrated.
A: Chargers can be ordered from your local Ophir distributor. For reference: 12 VDC, 500 mA, with the center pin being negative. The center must be negative for all but the Vega and Quasar which have the ability internally to switch the polarity to allow the use of different polarity power supplies.
A: The largest problem we see from equipment that is not working at top performance is contamination on the sensor. Dust or other contamination on the sensor surface can greatly impact the readings the sensor provides. When dust or other contaminations are on the sensor when it is illuminated by laser power/energy it can become "burned onto" the sensor. Simply blowing this contamination off before using the sensor can greatly reduce these problems and make the equipment perform at top performance for a longer period of time. Using canned air or dry nitrogen from a distance of 6 inches or more to lightly blow off the sensors can remove most of the contamination. Turn the sensor upside down so the surface the laser hits on is pointing to the floor. Start a light flow of air while pointed away from the sensor and lightly sweep it across the sensor without increasing the flow. This will lift most of the dust or other contamination from the sensor surface and gravity will continue to pull it to the floor.
A: The sensors with a continual response curve such as the ones listed above come with preset "favorite" wavelengths. If these "favorite" wavelengths do not match the application wavelength you are using they can be changed by performing the instructions below, which are for the Vega meter. For your specific meter, please see the User Manual.
While the Vega is off, plug in the head. Switch on the Vega.
From the main measurement screen, press "Laser" to select the correct laser
wavelength. If you want to save this new wavelength as the startup default, press
"Save" before exiting. If the wavelength you want is not among the wavelengths in the six
wavelengths listed and you want to change or add a wavelength, see step 3.
Changing Chosen Wavelengths:
From the power measurement screen select "Laser" and enter. Move to the
wavelength you wish to change or add. Press the right navigation key.
Using the up/down keys to change each number and the right/left keys to move
to the next number, key in the desired wavelength. Press the Enter key to exit. If
you wish to save this new wavelength as one of the 6 favorite wavelengths, press "Save".
Note: Saving the new wavelength in the Modify screen will not set this wavelength as the default
startup wavelength. To do so, you must follow the instructions in Step 2 above.
A: Ophir meters and sensors are calibrated independently. Each meter has the same sensitivity as the other within about 2 tenths of a percent. Each sensor is calibrated independently of a particular meter with its calibration information contained in the DB15 plug. When the sensor is connected to the meter, the meter reads and interprets this information. Since the accuracy of our sensors is typically +/-3%, the extra 0.2% error that could come from plugging into a different meter is negligible and therefore it does not matter which calibrated meter we use with a particular calibrated sensor.
A: The Nova II and Vega meters have a momentary push button switch to both turn them on and turn them off. The push button action to turn them on is a press-and-release-quickly action. The push button action to turn them off is a press-and-hold action, until the meter turns off.
A: The Vega, Nova II, StarLite, and Juno support the BeamTrack (PPS) sensors. All other instruments can display power and single-shot energy of a BeamTrack sensor, but do not display beam position and size at this time.
A: While you may order replacement batteries and replace them yourself, we recommend that you send the unit in for recalibration after replacement for best performance. Any time the case is removed from the meter, there is a potential for calibration factors and settings to be compromised.
A: First, clean the absorber surface with a Kleenex tissue, using one of the following cleaning agents, depending on the absorber. Then dry the surface with another tissue.
Please note the two absorbers in the table (Pyro-BB and 10K-W) cannot be cleaned with this method. Instead, simply blow off the dust with clean air or nitrogen. Don't touch these absorbers.
Note: These suggestions are made without guarantee. The cleaning process may result in scratching or staining of the surface in some cases and may also in some cases change the calibration
A: All absorbers used in power/energy measurement are not entirely flat spectrally, that is, they vary in absorption with wavelength. For this reason, Ophir measuring sensors are usually calibrated at more than one wavelength. If the absorption changes only slightly with wavelength, then we define wavelength regions such as <800nm, >800nm and give a calibration within these regions. In that case, the error in measurement between the wavelength the device was calibrated for and the measurement wavelength is assumed to be within the primary wavelength calibration error.
In other words, if you are measuring a wavelength that is different from the calibration wavelength, there is no added uncertainty, as long as the correct wavelength range is used.
A:Integrating Sphere Theory
Integrating spheres are used when we have divergent light sources. As shown in the illustration, an
integrating sphere has its inner surface coated with a surface that highly reflects (typically 99%) in a
scattering, nonspecular way. Thus when a divergent beam hits the walls of the integrating sphere,
the light is reflected and scattered many times until the light hitting any place on the walls of the
sphere has the same intensity.
A detector placed in the sphere thus gets the same intensity as anywhere else and the power the
detector detects is thus proportional to the total incident power independent of the beam divergence.
(The detector is so arranged that it only sees scattered light and not the incident beam).
An ideal integrating sphere has a surface with reflective properties are Lambertian. This means that
light incident on the surface is scattered uniformly in all directions in the 2pi steradians solid angle
above the surface. The surface used by Ophir closely approximates a Lambertian surface.
3A-IS Series The 3A-IS series has two 50mm integrating spheres in series with a photodiode detector. The two
series spheres scramble up the light very well thus giving output very independent of incident beam
divergence angle. The two spheres in series also insure that the light hitting the detector is greatly
reduced in intensity thus allowing use up to 3 Watts even though photodiodes saturate at about
1mW. There are two models, the 3A-IS with a silicon photodiode for 400 – 1100nm and the 3A-ISIRG
with an InGaAs detector for 800 – 1700nm
A: Libraries for Nova and LaserStar were developed in LabVIEW 6.1. They have been tested and found compatible with LabVIEW 7.0 and LabVIEW 8.6.1 as well.
The library for Nova-II, Vega, USBI, and Juno support (OphirInstr) was developed in LabVIEW 8.6.1 and has been tested with NI-VISA 4.6.2. It also includes support for the Single Channel LaserStar. This has been tested in LabVIEW 2009 as well.
The library for Pulsar support (DemoForPulsar) was developed in LabVIEW 7.0 and tested in LabVIEW 8.6.1 as well.
The new LabVIEW COM Demo that supports the Juno, Vega, Nova-II, Pulsar, and USBI devices was developed in LabVIEW 8.6.1 and has been tested in LabVIEW 2009 and LabVIEW 2010 as well
A: Device responses take the form 1.234 (a period distinguishes between the integer and fractional part of a real number). This may not match the settings of the computer upon which the VI is running. For example, many European countries use a comma (",") in place of a period (1,234). This causes the LabVIEW VI to not "understand" the devices's response.
(Go to http://zone.ni.com/devzone/conceptd.nsf/webmain/99d21982a9f954e186256a5b0057919e the section on Period and Comma Decimal Separators for National Instrument's explanation)
Solution: LabVIEW allows the User to override the local regional settings of the computer within the LabVIEW environment. To do so
A: At Ophir, we developed USB drivers for use with our StarLab application. National Instruments USB drivers work in a different manner. Ophir drivers are not compatible with NI VISA communication. NI drivers are not compatible with Ophir's StarLab application.
SwapINF configures Windows to associate the Ophir device with NI-VISA's usb driver (NIVIUSBK.sys) when LabVIEW is selected. It configures Windows to associate the Ophir device with the appropriate Ophir usb drivers (windrvr6.sys) when USBI is selected Note, this is only necessary for working with the OphInstr LabVIEW library. Other Ophir libraries do not make use of NI-VISA and therefore it is unnecessary to run SwapINF.
REMINDER: To work with LabVIEW, NI-VISA 4.6.2 or higher (from National Instruments) must also be installed.
Click here to download
the self-extracting "SwapINF Utility". Run the SwapINF utility
and follow the on-screen instructions to configure the USB speaking
device (USBI or Nova-II) for LabVIEW or USBI PC work as desired.
A: For customers using the new LabVIEW COM Demo, there is nothing additional to do. Just open it and get started. If writing your own LabVIEW application, make sure that the OphirLMMeasurement COM Object is included in your LabVIEW application
For customers using the legacy OphInstr LabVIEW package, here are additional clarification steps to assist establishing the interface to LabVIEW when connecting an Ophir meter such as the USBI/Nova II/Vega with the USB.
The sequence for preparing to interface the Ophir USBI (or meters connected through USB) with LabVIEW is generally as follows:
BE SURE the OPHIR CD is NOT in the PC CD drive when running SWAPINF.
Disconnect any USBI OPHIR Device from the PC
Run SwapINF utility
Set LabVIEW option On
Press "Swap" button
You will be prompted to "Remove the Ophir USBI Devices before continuing"
Press "OK" (you have already removed these)
Press "OK" again (after SwapINF is done)
Reconnect the Ophir USBI device to the PC that you wish to apply LabVIEW VI's on
If asked by Wizard (i.e. in XP) to update software etc.
Select "not this time" & press "next" button
Again, press "next" (install software automatically)
From here on you may apply LabVIEW VI's on your device
A: The Ophir integrating sphere sensors, models 3A-IS, 3A-IS-IRG and F100A-IS have a white diffuse reflecting coating on the inside of the integrating sphere. The sensitivity of the sensor is quite sensitive to the reflectivity of the coating. If the coating absorption goes up 1%, it can cause a 5% change in reading. Therefore, care must be taken not to soil or damage the white coating of the sensors. Also it may be a good idea to send the sensors for recalibration yearly.
A: The BC20 has a peak measurement and hold circuit
which measures the peak power on the detector and holds
it. Therefore when a beam is scanned over the detector,
when the beam is on the detector it goes up to a peak which
corresponds to the same power the detector would measure
if the beam was stationary and therefore the BC20 reads
the correct power whether the beam is scanned or not. In
order for the BC20 to do this, the beam must be on the detector
(of size 10x10mm) for at least ~13µs and therefore this
limits the scanning speed on the detector to 30,000 inch/s.
A: In general yes, but several technical issues need to be kept in mind (most of which are results of the fast physical response time of these sensors):
The pulse rate should be more than about 30Hz, otherwise the reading is unstable. At higher pulse frequencies, the sensor will respond as if the beam were CW.
It is possible for a pulsed beam to have average power within the sensor spec and yet have the energy of the pulses themselves be high enough to cause a momentary saturation of the sensor. It is important to be sure that pulse energy is also within sensor spec (the parameter "Max pulse energy" is included in all specs for the PD300 family, for just this reason).
The pulse width should not exceed about 500us.
The beam diameter should be no less than about 2mm .
The average power restriction in the spec should not be exceeded
Note: At the maximum pulse energy limit given in the spec, the reading will be saturated by about 5%, i.e. the reading will be about 5% lower than it should be. At 1/3 the maximum, the saturation will be about 1%.
A: Ophir's Photodiode PD-300, PD300-1W and PD300-3W series sensors offer automatic background subtraction so the measurement
is not sensitive to room light. With "filter out" (i.e. the external filter removed for low light measurements), 2 separate detector elements
are visible. The beam to be measured is incident only on the outer of the 2 detectors, but background light reaches both detectors.
The instrument will show the power measured by the outer detector minus that measured by the inner detector.
This patented method cancels out 95% - 98% of background light under normal room conditions, even if it is constantly changing.
A: Yes, the 5 default wavelengths are the discrete wavelengths that we have actually calibrated that sensor to NIST-Traceable standards. We have also run a spectrophotometer curve for that sensor and fitted that curve to the 5 discrete wavelengths that you see in the drop down menu. To set it to a wavelength that one needs (within its spectral bandwidth, i.e. 350-1100 nm for the PD300 and 200-1100 nm for the PD300_UV) one highlights one of drop down wavelengths in the drop down using the Down arrow key, and then you use the Right arrow selector to get into the menu for changing it. Then one uses the Up and Down and Right Arrow keys to select the wavelength that one wants to use it at. When done press SAVE and then SAVE again. Now it's stored in the E-PROM of the Smart Sensor connector and available for use. One can repeat the above procedure to store any 5 wavelengths that they use most often.
See the Video on how to change the sensor wavelength is now live on YouTube: http://www.youtube.com/watch?v=1qWXouQP18U
A: The PD300 sensors are not designed to measure with the fiber pushed up right against the detector surface. It may be reading lower in such a case due to saturation of the detector from the concentrated beam or higher due to back reflections off the detector and back again from the fiber tip. The optimal reading will be where the beam is expanded to a size of 2-5mm diameter. Therefore, you should back off the fiber to a distance where the beam has expanded somewhat. Do not back off too far, otherwise if the nominal beam size is larger than given above, you may lose some of the beam off the edges of the detector.
A: The PD300 series of photodiode-based sensors are calibrated with a full spectral curve using a scanning monochromator (plus a few laser "anchor points").
The wavelength ("Laser") setting tells the meter what wavelength is being used and hence what calibration factor to apply when a measurement is underway. It does not, however, physically limit the possibility of other wavelengths from entering. All light (within the sensor's specified range of course) entering the detector will be measured; the meter will apply the calibration factor meant for the selected wavelength, "thinking" that only that wavelength is present.
In other words, these sensors assume a monochromatic light source. Their relative spectral response is not flat and they are therefore not suited for broadband beams.
So, if you want to check one wavelength from a broadband source, you will need to use a wavelength filter that only passes that wavelength. Then you should set your meter to the appropriate wavelength to account for the detector's relative sensitivity.
A: The new Pyro-C sensors have a "user threshold" feature allowing the user to adjust the measurement threshold in noisy environments. Increasing the threshold will prevent triggering on noisy signals and allow accurate measurment of energy and frequency, as long as the laser pulses are larger than the noise.
The trigger level can be adjusted up to 25% of full scale, however operation depends on the pulse width setting. For pulse width settings below ~0.25ms, the minimum energy that can be measured accurately is approximately 40% above the user threshold setting. Pulses below this energy level will trigger the sensor down to the user threshold level, but accuracy is compromised.
For pulse width settings above ~0.25ms, accuracy is good all the way down to the threshold. If the laser pulse width is less than 1/2 the setting, the minimum energy corresponds to the setting. However, with longer laser pulse widths, the minimum energy will be higher, rising to approximately twice the user threshold level when the laser pulse width is equal to the sensor pulse width setting.
It is recommended always to set the user threshold to the minimum possible setting to retain best energy accuracy in any given situation. See the user manual for further information on how to use the user threshold.
A: All PE sensors are less accurate at a low percentage of full scale. Therefore it is always recommended to measure energies on the lowest range available (e.g. measure 1.8mJ on the 2mJ scale not the 20mJ scale). In order to get highest accuracy from your sensor, especially at low percentage of full scale, it should be zeroed against the meter the first time it is used with this meter. This is especially true for the PE-C series that can be used down to 3% of full scale if zeroed but can have an error of 2% at 10% of scale if not. The sensors are factory zeroed against the Vega/Nova II so need not be rezeroed if used with these types. If used with the Juno, Pulsar, USBI or LaserStar, they should be rezeroed. If zeroed with one type and then later used with a different type, they should be rezeroed the first time used with the different type.
A: All Ophir pyroelectric sensors can measure average power with Ophir Power and Energy Meters. The instrument measures the number of pulses each second and divides the energy reading by the pulse rate. If the pulse rate is constant, then the accuracy of power measurement will be the same as the energy accuracy since the pulse rate measurement is very accurate.
A: No, even though the scope adapter allows viewing of the actual electrical pulses coming out of the sensor and thus looking at higher repetition rates, the Power and Energy Meters is still needed to supply power to the sensor and to enable changing of ranges.
A: Ophir pyroelectric sensors have a positive temperature coefficient of 0.2% per degC which means that if the sensor heats up 10 degrees, the reading will be 2% high. The PD10 and PD10-pJ sensors use photodiode detectors so their temperature coefficient is the same as the PD300 sensors as listed on the PD300 pages of the Ophir catalog. The newest PE-C series of pyroelectric sensors (available June 2011) have a temperature sensor on board and a software correction for the heating effect so the reading is considerably more stable as the sensor heats up during use.
A: Our energy detectors measure the total energy deposited within a time window defined by the pulse width setting selected via the Power and Energy Meters. There is no minimum pulse width limitation since we are measuring the energy deposited, not power or peak power.
A: The sensor will stop integrating after the pulse width setting is reached and will lose part of the pulse. It will then read low. For instance if you try to measure a pulse width of 200us on a pulse width setting of 100us, the sensor will probably ready about 50% of the true energy.
A: The Power and Energy Meters simply decides it is time for a sample
and takes the next pulse that comes after that time, e.g.
if it samples at 400 Hz, then every 1/400th of a second
it is ready to take the next pulse that comes along.
A: The problem is most probably acoustic vibration. Pyroelectric sensors are sensitive to vibration as well as heat. On the most sensitive scales of sensitive sensors such as the PE9 and PE10, they may be very sensitive to vibration. Ophir sells a shock absorbing mounting post with rubber insulation to damp out vibrations from the table which may help. The part number is 7Z08268. The newer PE-C series of pyroelectric sensors have an adjustable threshold so you can set the threshold to a value above the noise level but below energies you want to measure and thus eliminate false triggering.
A: The problem is most probably false triggering caused by acoustic vibration. If the pulse frequency as shown on the meter jumps around, then acoustic vibration is almost certainly the problem. Pyroelectric sensors are sensitive to vibration, and they in fact detect acoustic pulses through the same physical mechanism with which they detect laser pulses. On the more sensitive scales of sensitive sensors such as the PE9 and PE10, they may be very sensitive to vibration. You can see this by setting such a sensor to a low energy scale (e.g. 2 mJ) and clapping your hand once, just above the sensor's surface; you will get a reading. The solution is to put an acoustically absorbing material such as a thin piece of soft foam plastic under the base of the sensor to damp out any vibration; acoustic noise carries primarily through the base (rather than through the air). Ophir also sells a shock absorbing mounting post (P/N 7Z08268) which may help. If you have the one of the newer PE-C series sensors, then set the user adjustable threshold to above the noise level to eliminate the false triggering.
A:Before using the pyroelectric sensor for power or energy measurement, check that your laser power, energy and energy density do not exceed the head ratings. Use the laser damage test slide that has been sent with your sensor at the laser energy you want to measure to make sure it does not damage.
Please check the included data sheet or check on the website for the same information;
With the pyroelectric head, you have been supplied a
test slide with the same coating as on your pyroelectric
detector. You can also obtain this slide from your
dealer. You should use this slide to test the damage
threshold with your laser pulses. If the slide is damaged,
then either enlarge your beam or lower the laser energy
until damage is no longer seen.
A: The catalog specification states the maximum power a sensor can be used with and without the heat sink. The purpose of the heat sink is to keep the sensor temperature below the maximum permitted at higher average powers. If you use the sensor for a short time only, on the order of 1-2 minutes at a time, you should be able to measure up to the higher power given in the spec even without the heat sink.
A: The new PE-C sensors use a different pin on the D15 connector for the voltage output from the sensor than the previous sensors. All other meters can accept the voltage on either of two pins, so they work with either the previous sensors or the PE-C series. But the Nova does not have this additional input. Therefore, in order for a Nova to work with the PE-C series, an adapter, Ophir P/N 7Z08272 has been made available. The adapter plugs between the D15 socket of the Nova and the D15 plug from the PE-C sensor. If you want to use the Nova RS232 PC adapter, this can be plugged in as well onto the PE-C adapter and used at the same time. Note that the Nova does not support all the new features of the PE-C family such as user threshold and 5 different pulse width settings but will support all the features that were available on the previous PE line.
All USB speaking devices (Juno, Pulsar and USB as well as the Vega and Nova-II Power and Energy Meters) can be controlled via our StarLab. This provides full remote control and measurement capabilities. In addition, system integrators can make use of the OphirLMMeasurement COM object for all of our USB speaking devices that are included in the application installation. Documentation and Examples in Visual Basic, LabVIEW are found in the "Automation Examples" sub-directory of your StarLab directory.
Note: ActiveX components (UsbX for USB Interface, Vega, and Nova-II; FastX for Pulsar) are still provided for legacy systems but do not support the latest features (no Juno support, no Windows 7 support)
For our legacy LabVIEW community of developers we continue to supply the Ophinstr and DemoForPulsar libraries to get your LabVIEW VI solution started.
The StarLab can support up to 8 sensors simultaneously. This can be through attaching 8 sensors to 8 different USB Interfaces, 8 sensors to 2 Pulsars or any combination in between. Note that when working with a large number of devices you may run out of ports on the PC. In that case, you must use a USB compliant Hub
The Analog output for Pyro sensor can measure up to 10 Hz. Therefore if you want to measure at a higher frequency (up to the maximum frequency of the sensor), you can connect the Scope Adapter for Pyro sensor (Ophir P/N 1Z11012). This adapter provide a BNC output to scope to see every pulse up to the maximum sensor frequency. Note: The Pulsar device is not equipped with an analog output
From StarLab, we support customer tailored OEM features as well as standard application features. If OEM is selected, the user will be asked to enter his OEM code. The OEM code is specific to each type of tailored interface ordered. If the code is entered, a special installation (with the requested features) will be performed. For all other customers, the Standard installation is the correct choice.
We have recently introduced 64 bit StarLab 2.40 application software (also compatible with 32 bit). This software package is free, and when combined with our USB-capable meters such as Vega or Nova II, or our USB based PC interfaces such as Juno, Pulsar and USBI, it is the ultimate in live data viewing, collection and analysis of laser power and energy measurements. If you want to go wireless, use it with our Bluetooth enabled Quasar. StarLab is a standalone software package that is very modular. Use it with up to 8 instruments or PC Interfaces to display and collect data from all 8 simultaneously. You can perform math functions for ratiometric measurements such as A/B, and math functions like A-B, A+B, or A *B. Display all on one coordinate system with a different color for each, or split them into several windows. View data in Line, Bar Graph, Histogram, or for tuning up one channel use our simulated analog meter with or without hysteresis. Get Live Statistics like Min, Max, Avg, and Std. Dev, or select batch size for stats. There's more:
Measure power and/or energy density , based on user defined beam size.
Time-synched multi-channel logs to a single log file for later review.
LabVIEW and Active X support.
If you have one of our instruments with USB or our USB interfaces download it for free now and try it out. There is no need to uninstall older versions of our USBI program if you are already using them and just want to try this out. If you don't have one of our instruments or USBI interfaces contact us, and set up a free demonstration in your lab or production floor.
Here's the link to download it:
You'll Love It like I do.
A: In general, the dynamic range, i.e. the ratio of maximum useable power to minimum useable power of Ophir OEM sensors is 40:1. If greater dynamic range is desired, Ophir OEM RS232 sensors are available with several selectable ranges.
A: The damage threshold of thermal sensors does depend on the power level and not only the power density because the sensor disc itself gets hotter at high powers. For instance, the damage threshold of the Ophir broadband coating may be 50KW/cm2 at 10 Watts but only 10KW/cm2 at 300W. The Ophir specifications for damage threshold are always given for the highest power of use of a particular sensor, something which is not done by most other manufacturers. This should be taken into account when comparing specifications.
A: We publish a nominal damage threshold for most
of our thermal BB sensors as 20KW/cm2. Other manufacturers
may quote higher numbers than this. In actuality, in one
to one tests against competitors, our sensors show a higher
damage threshold but the actual damage threshold depends
on the total power as well as the power density. For very
low powers such as 30W, the damage threshold can be as high
as 50KW/cm2 and at high powers such as 5KW, it drops to
3KW/cm2. The Ophir sensor finder program takes account of
these variations in its calculations.
A: The damage threshold curve in the sensors catalog
only goes down to 1ns but the energy damage threshold is
similar for shorter pulses. You can use ½ of the ns value
for fs pulses i.e. the absorber damages twice as easily.
A: For HE between 0.625 and 1um, the window transmits too much and the absorption drops by ~10%. Because of this, the thermal heat sink compound behind the absorber can dry out. If the power and energy is kept to 1/10 of maximum and the calibration is not important, the sensor can be used in this spectral region.
A: Thermal sensors for intermittent use such as models
30(150)A, L40(150)A etc. can be used up to the powers in
parenthesis for a period given approximately by the following
formula: The rule of thumb is that you can use the sensor
for 1 minute/watt/cm3 of sensor. So for 150 watts for 30(150)A
you have 1minute*165cm3/150watt =~ a little over one minute.
The sensor finder program calculates the allowability of intermittent
use when the user fills out the choice for duty cycle.
A: Water cooled sensors will not work properly at all
unless the sensor is filled with water to make thermal contact
between the disc and sensor. If the sensor is filled with water
and the input and output connectors are stopped up, then
the sensor can be used for a short time without water flow
or at much reduced power continuously. Note, however, that when used this way, the response time of the sensor may not be optimal and it may be slow or overshoot.
A: Water cooled sensors will hardly be affected by ambient temperature since the sensor temperature is determined by the water temperature. Ophir convection and fan cooled sensors are designed to operate in an ambient environment of 25degC up to the maximum rated power continuously. At this power, the sensors should not exceed about 75degC in temperature. If the room temperature is higher, then the maximum power should be derated accordingly. For example if the room temperature is 35degC, then the maximum power should be (75-35)/(75-25) = 80% of maximum rated power.
A: Surface Absorbers are spectrally broadband and spectrally flat due to their absorbing surface. With Surface Absorbers, the photons are converted to heat in the front layer of the absorbing surface.
The P versions of these sensors have a ground glass absorber. This provides superior damage resistance for high energy Q-switched type lasers, but has a low damage threshold for CW lasers. This type of sensor is referred to as a Volume Absorber; the laser energy is absorbed in the volume of the material below the front surface.
For a detailed discussion of thermal surface and volume absorbing sensors and absorbers for high power lasers, click here.
A: It is not recommended to choose a sensor if it is very close to the damage threshold if there is an alternative since laser damage is not an exact figure and depends on many things. Use the Sensor Finder to find the best match where you are preferably below 50% of the damage threshold.
A: The energy threshold (at which a thermal head will be triggered to begin a single pulse energy measurement) has 3 levels: HIGH - ~3% of full scale; MED - ~1% of full scale and LOW - ~0.3% of full scale. Sometimes the lowest energy range and LOW level give false triggering or missing pulses. In any case the standard deviation will be relatively higher in the threshold area. If the head is used in stable conditions, it is generally possible to measure single shot pulses below the specified limit, though its value will be less accurate.
A: It is not necessary to cool it with water all the time. However, when the water is turned on, there is a transient period where the reading is not stable until the sensor adjusts to the water flow. Therefore, turn on the water before applying the laser and wait until you get a stable reading close to zero before applying the laser. This can take up to 1 minute.
A: The answer to this question is two-fold. First of all the recalibration process accomplishes the recalibration of the sensor and returns it to "as-new" working condition. If there is surface damage on the sensor disc that creates areas of non-uniformity exceeding the uniformity across-the-surface specification, then the disc needs to be replaced, even though the accuracy performance of the sensor is not out-of-tolerance. Secondly, many applications require that sensors be found in-tolerance during the calibration process, or else deviation explanations are required and/or costly recalls may need to be implemented. The calibration process is intended to help maintain the sensors within tolerance if at all possible.
A: There are a number of options, depending on the purpose.
In many cases, the simplest solution could be to make use of the analog output of the meter – that gives a voltage signal proportional to the actual reading (it is in fact just a D/A translation of what is being displayed), so it represents a fully calibrated reading. The full scale value is a function of the meter being used and the power range it is on.
2. The "SH to BNC connector" (Ophir P/N 7Z11010) simply takes the raw output from the detector element and sends it to the scope. It bypasses the sensor's EEROM which contains the calibration data, so it essentially turns the sensor into an uncalibrated "dumb" analog sensor. It should be noted, though, that in some cases we could be talking about a signal to the scope that may be low, perhaps even near the noise level of the scope, which limits the usefulness of this method at low powers.
If the need is to see the pulse width – the temporal profile – the solution (assuming applicable specs) is to use the FPS-1 connected to a scope; you can point it anywhere where it will catch some backscatter from your laser, and you'll see the pulse temporal form as it really is.
A: The thermal sensor works by measuring the heat flowing through its sensor. When measuring a short pulse, the heat is absorbed in the sensor
absorber and then flows out through the sensing elements. The integral of this heat flow is a measure of the energy. Thus the sensor is actually
measuring the energy that flows after the pulse is finished and the pulse width does not matter for this measurement.
A: The Ophir BeamTrack series of Power/Position/Size meters may be just the thing. In addition to all the things an ordinary power/energy meter does, the BeamTrack will measure the beam position and size as well to a precision of ~0.1mm. For a gaussian beam it will give you the actual beam waist diameter and for other beams it will give a relative number that changes with beam size. See http://www.youtube.com/watch?v=U2oliO-Cz8M for a demo of the BeamTrack.
A: Ophir "Thermal" detectors have flat regions of response over their entire usable range. Ophir does a calibration for this flat region and when the detector is no longer flat it gets a new calibration for this new flat region. This is why there are regions instead of discrete wavelengths.
A: The StarLab OEM installation option is only for customers who have requested and paid for special custom software features. Always select the StarLab Standard installation option, unless you are the customer who has purchased the special OEM option.
You absolutely can use the Quasar to do data collection, but how similar the process will be depends on the type of sensor being used. If you are using Ophir Thermopile and Photodiode sensors, these work much the same way on the Quasar as they do on the Nova-II. You should be able to collect data in much the same way as you do today. You just need to establish a Bluetooth connection, open a COM port on the PC, and then can send commands as with the Nova II. You might need a small amount of low level code just to send/receive the commands and strip the prefix/suffix, which is not difficult. Ophir-Spiricon tech support can help. If you are using Pyroelectric sensors, however, you will have to wait for the ActiveX package to be released, because the communications are very different from the Nova II, and you will not be able to handle the data on your own. Your data collection software might be somewhat different, as well, but it will function similarly to the Pulsar. ActiveX for the Quasar is tentatively scheduled for the beginning of 2009. Note also the "every pulse" data rate on the Quasar with a Pyro sensor will be lower than on the Nova II; we guarantee 500 pulses/second in our spec.
The Quasar is no different than the other instruments that have electronic components: it requires annual recalibration. But it’s up to the customer whether to do this or not. We know that the calibration of the instruments degrades somewhat over time, as shown in the datasheet. This may or may not affect your particular application. To maintain compliance with ISO and other standards, we highly encourage annual recalibration.
Unfortunately, this is not possible, at this point. The Quasar can establish a connection with only one host PC at a time. If you connect to the laptop in the clean room, you will not be able to then connect to another PC in an adjacent office; the Quasar will be locked out. You would have to cut the connection on the laptop before you could establish the connection to the second PC. On the other hand, the beauty of the Quasar is that you can ONLY connect to the second PC in the adjacent room, outside the clean room, and log all the data from there. There is no need for a laptop in the clean room, unless of course, if you need to observe data while in there, in which case you would have to do the above.
In actual testing done at customer sites, using the high power option, there was not a place within 100 meters that we could not connect, including going through multiple walls that were made of drywall. The only time we lost transmission was when the walls were made of concrete or we had to pass through some metal doors. With normal labs and offices the signal went right through. In several cases, including a solar power scribing application where windowed doors had to be closed, we were getting a continuous connection as we walked around the spacious building into offices and labs. With the standard range option, the range should be about 1/3 of this i.e. 30 meters.
Quasar runs on Bluetooth, the 2.4-2.5GHz "ISM" band (ISM = Industrial, Scientific and Medical). This is the same band used by WiFi and other technologies. This frequency was chosen as it is available without restrictions around the world. Because other technologies also use it, Bluetooth has to be designed to tolerate interference from other sources. It does this by swapping between 79 channels, at 2.402GHz up to 2.480GHz (each channel is 1MHz). This type of modulation is called FHSS, Frequency Hopping Spread Spectrum. If data does not get through on one channel it retries on a different channel. Other technologies, such as WiFi, use different techniques.
This design makes Bluetooth very robust. In principle, if there is another radio transmitter nearby that is using the same 2.4-2.5GHz band AND using the same modulation scheme, interference is a possibility, but not a real likelihood. If the other transmitter is using a different band, there should not be a problem, because there is very little interference produced at other higher or lower frequencies - this is checked during qualification of these devices for CE and FCC in RF test labs.
In general, Bluetooth is in common use everywhere, by cellular phone headsets, for example, so interference is not normally a significant risk factor.
Yes, we have an Android app that you can download from the Android Market place to run your Quasar on your Android device. Search for Ophir Optronics Quasar. You need to be running Android 2.3.3 or higher.