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current will be converted to a voltage as 0.5mA * 50Ω, or 25mV. The 10μW power level will produce on output
voltage of 20μA * 50Ω, or 1mA. For some measurement devices this signal level may be too low and a
compromise between battery lifetime and measurement accuracy will need to be made.
As a result, when using a biased photodetector with a battery powered source it is beneficial to use as low of
light intensity as is reasonable for the application. It is important to remember that a battery will not immediately
cease producing a current after it has supplied its specified number of mAhr; instead, the terminal voltage of
the battery will drop below the rating of the battery. A drop in the terminal voltage of the battery will lower the
electric potential being applied to the photodiode. This in turn will increase the response time of the detector
(lower the bandwidth of the detector). As a result, it is important to make sure that the battery is operating
within its specified parameters in order to ensure the proper functioning of the biased photodetector. The
battery can be tested by following the procedure described in the specifications sheet for the detector.
Another suggestion to increase the battery lifetime is to remove, or power down the light source illuminating the
sensor. Without the light source the photodetector will continue to draw current equal to the photodetector dark
current, however this will significantly increase the lifetime. The SV2 has a dark current less than 0.005nA, will
not significantly impact the battery life.
For applications where a DET series photodetector is being continuously illuminated with a relatively high-
power light source or if having to change the battery is not acceptable consider using the DET1A adapter for
that allows the photodetector to be powered using the LDS2 power supply. The drawback to the DET1A is that
noise in the line voltage will contribute to noise in the output signal of the DET series detector.
All high-speed photodetectors are under warranty for 12 months. During this time, Thorlabs
will accept return and repairs free of charge for all problems, provided the customer operates the unit
within our specifications. Replacement batteries are available directly from Thorlabs, part # SBP20.
The average time for repair and returns is 2 weeks.
You may use any of the following methods to contact Thorlabs in case of difficulty or if you
have questions regarding your photodetector.
techsupport@thorlabs.com
Fax:
(973)300-3600
Phone:
(973)579-7227
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Warranty Information and Technical Support
You can send a detailed email message and one of our application
engineers will respond promptly (within 1 business day).
2811-S02 Rev H 6/12/08
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