tinska.h
Junior Member level 2
Greetings,
I have made a LIA to measure IR signal amplitude in a optically noisy environment. However even in a relatively quiet environment I get +/-5 mV fluctuations in to my readings. Signal is approx. 450mV. I don't know if this is a good or bad LIA performance?
Here is my setup:
- IR light source is switching on and off at 1kHz freq. (Squarewave)
- Vishay BPV10NF PIN Photodiode -> transimpedance amplifier (AD8616) at 100k Gain -> Passive HPF -> 16bit ADC
- 1kHz reference square signal
- 20kHz sampling frequency
1. Multiplying signal data (10 000 samples) with Sin and Cos (IQ-demod)
2. Instead using LPF I'm just averaging I and Q chunks
3. Then get the result by Sqrt(I^2 + Q^2) and normalizing it
I've never used a commercial LIA before (or any LIA), but I would assume that LIA should be stable and not show random fluctuations.
Is there any ideas how to improve? Or am I doing anything wrong? Should I be implementing a FIR LPF instead just averaging?
Thanks in advance
I have made a LIA to measure IR signal amplitude in a optically noisy environment. However even in a relatively quiet environment I get +/-5 mV fluctuations in to my readings. Signal is approx. 450mV. I don't know if this is a good or bad LIA performance?
Here is my setup:
- IR light source is switching on and off at 1kHz freq. (Squarewave)
- Vishay BPV10NF PIN Photodiode -> transimpedance amplifier (AD8616) at 100k Gain -> Passive HPF -> 16bit ADC
- 1kHz reference square signal
- 20kHz sampling frequency
1. Multiplying signal data (10 000 samples) with Sin and Cos (IQ-demod)
2. Instead using LPF I'm just averaging I and Q chunks
3. Then get the result by Sqrt(I^2 + Q^2) and normalizing it
I've never used a commercial LIA before (or any LIA), but I would assume that LIA should be stable and not show random fluctuations.
Is there any ideas how to improve? Or am I doing anything wrong? Should I be implementing a FIR LPF instead just averaging?
Thanks in advance