The FL250A-BB-50 thermopile sensor is a general purpose fan cooled laser power and energy thermal sensor with a 50 mm aperture. It can measure optical power from 150 mW to 250 W and energy from 80 mJ to 300 J. It has the spectrally flat broadband BB coating and covers the spectral range from 0.19 to 11 µm.
Broadband 0.19 to 11 µm absorber
Fan-cooled for 0.15-250 W average power measurement
If you need to measure beam position or size in addition to power, we offer the FL250A-BB-50-PPS BeamTrack version of this sensor.
fl250a-bb-50-thermopile-sensor - Drawings & CAD
Additional CAD file downloads are not available for this product.
fl250a-bb-50-thermopile-sensor - Drawings
Additional drawings are not available for this product.
Specifications
Product Name
FL250A-BB-50
Absorber Type
BB - Broadband general purpose
Aperture Size
Ø50 mm
Spectral Range
0.19-11 µm
Minimum Power
150 mW
Maximum Average Power
250 W
Minimum Pulse Energy
80 mJ
Maximum Pulse Energy
300 J
Response Time
2.5 s
Maximum Average Power Density
10 kW/cm²
Maximum Energy Density <100 ns
0.3 J/cm²
Maximum Energy Density 2 ms
10 J/cm²
Cooling
Fan
Dimensions
90 x 90 x 105 mm (LxWxD)
Cable Length
1.5 m
CE Compliance
Yes
UKCA Compliance
Yes
China RoHS Compliance
Yes
Features
Choosing a Thermal Sensor
In this short “Basics” video we review the use – and selection - of thermal sensors for measuring low, medium and high laser powers.
How to Measure Power of Broadband Sources
This video explains how to use Ophir sensors and meters to measure the power or energy of broadband light sources such as solar radiation, flash lamps, LEDs, etc.
Thermal Power Sensor Accuracy
Ophir former CTO Dr. Ephraim Greenfield discusses the various factors that contribute to uncertainties in measurement when using Ophir laser power and energy meters.
Effects of Incidence Angle on Measurements
In this video, you will learn to what degree a beam’s incidence angle matters, and for which sensor types this should be taken into account.
Thermal Sensor Calibration
As the spectral sensitivity of the absorber used for the power and energy measurement is not fully linear, Ophir sensors get a high precision calibration by default with more than one wavelength.
Each thermal sensor is calibrated independently of a particular Ophir power 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 to display a calibrated reading. Each power meter is calibrated independently and has the same sensitivity as an other meter within about 2 tenths of a percent.
Unless otherwise indicated, Ophir sensors and meters should be recalibrated within 18 months after initial purchase, and then once a year after that.
Absorption of different thermal sensor absorber types
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.
The Ophir specification on accuracy is in general 2 sigma standard deviation. This means, for instance, that if we list the accuracy as +/-3%, this means that 95% of the sensors will be within this accuracy and 99% will be within +/-4%. For further information on accuracy see calibration procedure tutorial.
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. The Sensor Finder takes the power level into consideration when calculating damage threshold.
First, clean the absorber surface with a tissue, using Umicore #2 Substrate Cleaner, acetone or methanol. Then dry the surface with another tissue. Please note that a few absorbers (Pyro-BB, 10K-W, 15K-W, 16K-W and 30K-W) cannot be cleaned with this method. Instead, simply blow off the dust with clean air or nitrogen. Don't touch these absorbers. Also, HE sensors (such as the 30(150)A-HE-17) should not be cleaned with acetone.
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 change the calibration.
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 25°C up to the maximum rated power continuously. When operating at its maximum rated power, the sensor’s body should typically not exceed about 80°C in temperature.
Note: If the room temperature is higher than 25°C, then the maximum power (at which the sensor can be safely operated) should be derated accordingly from the specified maximum (since dissipation of the heat from inside the sensor to the surrounding air will be more difficult). For example, if the room temperature is 35°C, then the maximum power limit should be (80-35)/(80-25) = 82% of maximum rated power as given in the sensor’s spec.
In theory, if a beam is completely parallel and fits within the aperture of a sensor, then it should make no difference at all what the distance is. It will be the same number of photons (ignoring absorption by the air, which is negligible except in the UV below 250nm). If, nevertheless, you do see such a distance dependence, there could be one of the following effects happening:
If you are using a thermal type power sensor, you might actually be measuring heat from the laser itself. When very close to the laser, the thermal sensor might be “feeling” the laser’s own heat. That would not, however, continue to have an effect at more than a few cm distance unless the light source is weak and the heat source is strong.
Beam geometry – The beam may not be parallel and may be diverging. Often, the lower intensity wings of the beam have greater divergence rate than the main portion of the beam. These may be missing the sensor's aperture as the distance increases. To check that you'd need to use a profiler, or perhaps a BeamTrack PPS (Power/Position/Size) sensor.
If you are measuring pulse energies with a diffuser-based pyroelectric sensor: Some users find that when they start with the sensor right up close to the laser and move it away, the readings drop sharply (typically by some 6%) over the first few cm. This is likely caused by multiple reflections between the diffuser and the laser device, which at the closest distance might be causing an incorrectly high reading. You should back off from the source by at least some 5cm, more if the beam is not too divergent.
Needless to say, it’s also important to be sure to have a steady setup. A sensor held by hand could easily be moved around involuntarily, which could cause partial or complete missing of the sensor’s aperture at increasing distance, particularly for an invisible beam.
Pin fins can cool the same laser power to a lower temperature or take higher power in the same size sensor. Take the FL250A sensor, for example, used with a 250 W laser: The old version would reach 74 °C at maximum power, while the new only reaches 55 °C.
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.
The Ophir specification on accuracy is in general 2 sigma standard deviation. This means, for instance, that if we list the accuracy as +/-3%, this means that 95% of the sensors will be within this accuracy and 99% will be within +/-4%. For further information on accuracy see calibration procedure tutorial.
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. The Sensor Finder takes the power level into consideration when calculating damage threshold.
First, clean the absorber surface with a tissue, using Umicore #2 Substrate Cleaner, acetone or methanol. Then dry the surface with another tissue. Please note that a few absorbers (Pyro-BB, 10K-W, 15K-W, 16K-W and 30K-W) cannot be cleaned with this method. Instead, simply blow off the dust with clean air or nitrogen. Don't touch these absorbers. Also, HE sensors (such as the 30(150)A-HE-17) should not be cleaned with acetone.
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 change the calibration.
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 25°C up to the maximum rated power continuously. When operating at its maximum rated power, the sensor’s body should typically not exceed about 80°C in temperature.
Note: If the room temperature is higher than 25°C, then the maximum power (at which the sensor can be safely operated) should be derated accordingly from the specified maximum (since dissipation of the heat from inside the sensor to the surrounding air will be more difficult). For example, if the room temperature is 35°C, then the maximum power limit should be (80-35)/(80-25) = 82% of maximum rated power as given in the sensor’s spec.
In theory, if a beam is completely parallel and fits within the aperture of a sensor, then it should make no difference at all what the distance is. It will be the same number of photons (ignoring absorption by the air, which is negligible except in the UV below 250nm). If, nevertheless, you do see such a distance dependence, there could be one of the following effects happening:
If you are using a thermal type power sensor, you might actually be measuring heat from the laser itself. When very close to the laser, the thermal sensor might be “feeling” the laser’s own heat. That would not, however, continue to have an effect at more than a few cm distance unless the light source is weak and the heat source is strong.
Beam geometry – The beam may not be parallel and may be diverging. Often, the lower intensity wings of the beam have greater divergence rate than the main portion of the beam. These may be missing the sensor's aperture as the distance increases. To check that you'd need to use a profiler, or perhaps a BeamTrack PPS (Power/Position/Size) sensor.
If you are measuring pulse energies with a diffuser-based pyroelectric sensor: Some users find that when they start with the sensor right up close to the laser and move it away, the readings drop sharply (typically by some 6%) over the first few cm. This is likely caused by multiple reflections between the diffuser and the laser device, which at the closest distance might be causing an incorrectly high reading. You should back off from the source by at least some 5cm, more if the beam is not too divergent.
Needless to say, it’s also important to be sure to have a steady setup. A sensor held by hand could easily be moved around involuntarily, which could cause partial or complete missing of the sensor’s aperture at increasing distance, particularly for an invisible beam.
Pin fins can cool the same laser power to a lower temperature or take higher power in the same size sensor. Take the FL250A sensor, for example, used with a 250 W laser: The old version would reach 74 °C at maximum power, while the new only reaches 55 °C.
Accessories
Fiber Connector Adapters
These adapters allow for power measurement of connectorized fiber-optic cables. The sensor may need an additional mounting bracket to connect to these fiber adapters.
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Description
Compatibility
Drawings, CAD & Specs
Avail.
Price
7Z08227SC Fiber Connector Adapter, Power and Energy Sensors
UNIVERSAL
In Stock
$302
7Z08226ST Fiber Connector Adapter, Power and Energy Sensors
UNIVERSAL
In Stock
$264
7Z08229FC Fiber Connector Adapter, Power and Energy Sensors
UNIVERSAL
In Stock
$153
1G01236ASMA Fiber Connector Adapter, Power and Energy Sensors
UNIVERSAL
In Stock
$74
Showing 1 to 4 of 4 entries
Fiber Adapter Mounting Bracket
A mounting bracket is needed to connect most thermal sensors to a fiber adapter (SC, ST, FC or SMA). This bracket can be used for fan-cooled thermal sensors with a 50mm diameter.
Order a cable of a different length along with the sensor to receive a cable other than the standard 1.5 m length.
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Drawings, CAD & Specs
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Price
7E01122AThermal Sensor Cable, 3 m Length, Connect to Power Meter
UNIVERSAL
In Stock
$112
7E01122BThermal Sensor Cable, 5 m Length, Connect to Power Meter
UNIVERSAL
In Stock
$112
7E01122CThermal Sensor Cable, 10 m Length, Connect to Power Meter
UNIVERSAL
In Stock
$167
7E01122DThermal Sensor Cable, 12 m Length, Connect to Power Meter
UNIVERSAL
7 Weeks
$167
Showing 1 to 4 of 4 entries
Sensor Connector to BNC Adapter
The SH to BNC Adapter allows the connection of an Ophir sensor to a current or voltage measuring device for measurement of the raw sensor analog output. A current meter should be used for photodiode sensors. Current or voltage meters can be used for thermal sensors.
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Drawings, CAD & Specs
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7Z11010BNC Adapter, DB15 Optical Sensor Connector
UNIVERSAL
In Stock
$92
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Extended Warranty for Sensor
Customers that purchase the above items also consider the following items. Ophir-Spiricon meters and sensors include a standard manufacturers warranty for one year. Add a one year Extended Warranty to your meter or sensor, which includes one recalibration.
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