Hello guys, I'm actually trying to build one ultraviolet flame sensor just as a part of my hobbies and I'm encountering few issues lately and I'm hoping that I could get some answers to address the following issues:

1. When I built this circuit on a PCB and tried to test it, I'm getting few Milli-volts of offset or noise by measuring it with a multi-meter at the output of arduino port I.e at A1 and A2. My first question is how to reduce this noise or offset so as to get zero volts without giving any input.
2. When I'm trying to interface with ADS1115 I'm getting an offset of 187 Milli-volts . But it is OK to get 187 milli-volts because thats the least noise that it can generate. when I tried to execute and run the code by default I should be getting 187 milli-volts but instead a few times I'll be getting 187 milli-volts and some times even double or triple of that value. My second question is how to address this issue so as to get complete zero volts or atleast a constant reading of 187 milli-volts without giving any input to the circuit.
3. My last question is how do I set threshold value for my ultraviolet flame so that it only reacts to UV light and not to any solar radiation or IR radiation.

I'm using LMC6001 as a trans-impedance amplifier with gain as 100 Mega Ohm and capacitor of 1 pico Farad. Also I have used ADS1115 in the circuit to get high resolution readings. I have attached my circuit diagram and my arduino code below.

Kindly share your thoughts and knowledge. Thank you.

 

what is the gain of the input op amps ?
are you using low noise amps ?
How is the output of the amps connected to the arduino input ? what is the ads1115 meant to do ?
could you not just connect the op amp outputs to separate analog inputs of the Arduino ?


what is the noise on the power supplies of the op amps ?
those charge pump chips are generally very noisy

 

Why are you using a noisy LT1054 negative voltage generator? The LMC6001 opamps do not need a negative supply (use ground) and work fine from a +5V supply.
Maybe your UV detector picks up background UV from your environment?
EDIT: what is the make and model number of your UV detector?