Professor601
New Member
Greetings, all.
I have a Picxe 18M2 I am using to read a temperature from a thermopile, running the thermopile through a basic op-amp to get the voltage to a usable level. For both readadc and readadc10 the data varies widely, by a range of 15 or more in debug on the readadc command (i.e. 8-bit resolution). The voltage from the op-amp is much steadier than that when tested with a voltage meter, though it does vary by 2-3 thousandths of a volt. (e.g. from .752 - . 755 volts). I have read that the FVR can vary by a bit, so I wondered if that might be it, but a potentiometer hooked in to the chip on readadc is rock solid, and a different sensor (a Hall effect sensor) run through the same op-amp is also quite stable.
So, any ideas on how to stablise the reading from the thermopile, or at least any thoughts why a thermopile would be so wonky? Specific chip data is listed below if that helps any.
Courteously,
The Professor (601)
Picaxe 18M2
ZTP135 thermopile (optical remote temp sensor)
LM358N dual channel op amp
470k (total) to 1k resistor multiplier on the op amp
All running on 4.5v battery pack
I have a Picxe 18M2 I am using to read a temperature from a thermopile, running the thermopile through a basic op-amp to get the voltage to a usable level. For both readadc and readadc10 the data varies widely, by a range of 15 or more in debug on the readadc command (i.e. 8-bit resolution). The voltage from the op-amp is much steadier than that when tested with a voltage meter, though it does vary by 2-3 thousandths of a volt. (e.g. from .752 - . 755 volts). I have read that the FVR can vary by a bit, so I wondered if that might be it, but a potentiometer hooked in to the chip on readadc is rock solid, and a different sensor (a Hall effect sensor) run through the same op-amp is also quite stable.
So, any ideas on how to stablise the reading from the thermopile, or at least any thoughts why a thermopile would be so wonky? Specific chip data is listed below if that helps any.
Courteously,
The Professor (601)
Picaxe 18M2
ZTP135 thermopile (optical remote temp sensor)
LM358N dual channel op amp
470k (total) to 1k resistor multiplier on the op amp
All running on 4.5v battery pack