Gain setting on Optometer, what does it do?

[nordmoon]

I have an optometer, which I have used to measure the laser power (using integrating sphere and detector).

My question is what does it mean with having the setting "auto gain" of 10?
Should I have used a gain = 1?
I did get results as I expected, but I am unsure what the gain setting means on a optical power meter?

 

[DaveC426913]

I have no specific answer to your question, but I always thought gain referred to an absolute amplification by literally adding power. i.e. the noise is amplified as much as the signal.

For example, if the return was too weak that it fell below the threshold of the sensor, you'd get no signal reported at all. But turn up the gain, and at least the signal would get through, even if it came at the cost of a proportional increase in noise.I think, ideally, you want the gain as low as you need it to be while still receiving a signal.

I think another function of gain is to put the signal in the most sensitive range for the detector.

Here is an example of too much gain:
https://www.wpiinc.com/clientuploads/stories/amp_offset.jpg
I am merely a layperson, so I cannot speak with any certainty.

 

[berkeman]

I have an optometer, which I have used to measure the laser power (using integrating sphere and detector).

My question is what does it mean with having the setting "auto gain" of 10?
Should I have used a gain = 1?
I did get results as I expected, but I am unsure what the gain setting means on a optical power meter?

Can you post the datasheets of the instruments in your setup? It may be meant to correct for the gain of the preamplifier, for example.

Like when you use some current probes with oscilloscopes, the probe reports its gain settings to the 'scope, so the 'scope can display the corrected (and correct) current levels...

http://tmi.yokogawa.com/images/uploaded/701928_29_2.jpg