Lock-in Amplifier bandwidth

[evandrorech]

Hi!

I'm trying to control a simple magnetic levitation system using myRIO. For the displacement sensor, I'm using a IR emmiter/receiver pair in the bottom, and measuring the intensity of the received IR, I get the position.

The sensor have some problems, a little noise, and a big interference from sunlight, so I thought about using a lock-in amplifier and switch the IR emmiter. Looking at the Lock-in toolkit, the time constant of the output filter in the example is about 100ms, but I need a fast feedback, so I think the time constant need to be between 250us and 1ms, is that possible? I'll eliminate the offset caused by sunlight that way?

Thanks!

[MeasurementsMan]

Hi Evan,

There are two very big caveats here:

1. If the signal from the sunlight is so strong that it saturates the input amplifier or the ADC, there is no way to recover the signal of interest.

2. You can change the time constant to smaller values, but you are giving up resolution as you do this.  1ms may be possible, but I don't know about 250us, especially with myRIO which only has 12 bit ADCs.  Since the toolkit is free, I suggest you try it out and post your results here

Best Regards,

MeasurementsMan

[evandrorech]

Thanks!

When I tested the sensor first time, the sunlight reduced my signal by a half or more, but don't saturate the sensor, so it's good!

I'll give a try as soon I can to verify the filters, and I'll post the results like you said!

Thanks again and best regards!

Evandro