Broadband 250 W Fan-Cooled Thermopile Sensor with 35 mm Aperture

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Overview

The FL250A-BB-35 thermopile sensor is a general purpose fan cooled laser power and energy thermal sensor with a 35 mm aperture. It can measure optical power from 150 mW to 250 W and energy from 50 mJ to 300 J. It has the spectrally flat broadband BB coating and covers the spectral range from 0.19 to 20 µm.

Broadband 0.19 to 20 µm absorber
Fan-cooled for 150 mW to 250 W average power measurement
50 mJ to 300 J pulse energy measurement

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Products

		Compare	Model	Compatibility	sortOrder	rankScore	ranking	Drawings, CAD & Specs		Absorber Type	Aperture Size	Minimum Power	Maximum Average Power	Availability	Featured Item	Price		Brand
		7Z02728 FL250A-BB-35 Thermal Laser Power Sensor, BB Type, 150 mW to 250 W, Ø35 mm, 0.19-20 µm $1,729 In Stock	7Z02728 FL250A-BB-35 Thermal Laser Power Sensor, BB Type, 150 mW to 250 W, Ø35 mm, 0.19-20 µm	UNIVERSAL	0.0	1.0	0.0		0.0	BB - Broadband general purpose	Ø35 mm	150 mW	250 W	In Stock		$1,729		Ophir

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Specifications

Product Name

FL250A-BB-35
Absorber Type

BB - Broadband general purpose
Aperture Size

Ø35 mm
Spectral Range

0.19-20 µm
Minimum Power

150 mW
Maximum Average Power

250 W
Minimum Pulse Energy

50 mJ
Maximum Pulse Energy

300 J
Response Time

2 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

64 x 64 x 95 mm (LxWxD)
Cable Length

1.5 m
CE Compliance

Yes
UKCA Compliance

Yes
China RoHS Compliance

Yes

Specifications

Product Name

FL250A-BB-35
Absorber Type

BB - Broadband general purpose
Aperture Size

Ø35 mm
Spectral Range

0.19-20 µm
Minimum Power

150 mW
Maximum Average Power

250 W
Minimum Pulse Energy

50 mJ
Maximum Pulse Energy

300 J
Response Time

2 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

64 x 64 x 95 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

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.

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

Frequently Asked Questions

How should I clean my sensor?
Answer
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.

When an accuracy spec is given, what exactly is meant?
Answer
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 and knowledge center.

How is the performance of thermal sensors affected by ambient temperature?
Answer
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.

Must I use a particular sensor only with the meter it was ordered with?
Answer
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.

Does the damage threshold depend on power level?
Answer
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.

Ophir thermal sensors have pin fins for cooling. They used to be cooled by flat fins. What's the difference?
Answer
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.

Do I need to recalibrate my instrument? How often must it be recalibrated?
Answer
Unless otherwise indicated, Ophir sensors and meters should be recalibrated within 18 months after initial purchase, and then once a year after that.

Can a laser measurement depend on the distance from the laser to the sensor?
Answer
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.

Frequently Asked Questions

How should I clean my sensor?
Answer
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.

When an accuracy spec is given, what exactly is meant?
Answer
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 and knowledge center.

How is the performance of thermal sensors affected by ambient temperature?
Answer
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.

Must I use a particular sensor only with the meter it was ordered with?
Answer
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.

Does the damage threshold depend on power level?
Answer
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.

Ophir thermal sensors have pin fins for cooling. They used to be cooled by flat fins. What's the difference?
Answer
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.

Do I need to recalibrate my instrument? How often must it be recalibrated?
Answer
Unless otherwise indicated, Ophir sensors and meters should be recalibrated within 18 months after initial purchase, and then once a year after that.

Can a laser measurement depend on the distance from the laser to the sensor?
Answer
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.

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.

Description	Compatibility	Avail.	Price
7Z08227 SC Fiber Connector Adapter, Power and Energy Sensors	UNIVERSAL	In Stock	$302
7Z08226 ST Fiber Connector Adapter, Power and Energy Sensors	UNIVERSAL	In Stock	$264
7Z08229 FC Fiber Connector Adapter, Power and Energy Sensors	UNIVERSAL	In Stock	$153
1G01236A SMA Fiber Connector Adapter, Power and Energy Sensors	UNIVERSAL	In Stock	$74

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 thermal sensors with a 35mm diameter.

	Compare	Description	Compatibility	Drawings, CAD & Specs	Avail.	Price
		7Z08265 Fiber Adapter Mounting Bracket, L50/FL250 Thermal Sensors	UNIVERSAL		In Stock	$144

N Polarity Power Supply/Charger

Power Supply/Charger for Centauri, Vega, Nova II, LaserStar, Nova, EA-1, Pulsar, Quasar, 6K-W, 120K-W and fan cooled sensors.

	Compare	Description	Compatibility	Drawings, CAD & Specs	Avail.	Price
		7E05029 N Polarity Power Supply/Charger DC Power Supply / Charger, N Polarity	UNIVERSAL		In Stock	$52

Thermal Sensor Cables

Order a different length cable along with sensor to receive a different cable than the standard 1.5 m cable.

Description	Compatibility	Avail.	Price
7E01122A Thermal Sensor Cable, 3 m Length, Connect to Power Meter	UNIVERSAL	In Stock	$112
7E01122B Thermal Sensor Cable, 5 m Length, Connect to Power Meter	UNIVERSAL	In Stock	$112
7E01122C Thermal Sensor Cable, 10 m Length, Connect to Power Meter	UNIVERSAL	In Stock	$167
7E01122D Thermal Sensor Cable, 12 m Length, Connect to Power Meter	UNIVERSAL	In Stock	$167

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.

	Compare	Description	Compatibility	Drawings, CAD & Specs	Avail.	Price
		7Z11010 BNC Adapter, DB15 Optical Sensor Connector	UNIVERSAL		In Stock	$92

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.