K8055, thermocouple voltage, labview, winxp se3

Kits PC Related Projects
1

Hi,

I am buiding a thermopile using the velleman K8055.

The themocouple is connected to the analogue input and ground and is supposed to generate a voltage in the range of mV. I use labview link library to read the dll but I do not get any reply when i set to readallanalogue.

I scoured the whole forum on K8055 and temperature sensing but no one seem to be using thermopiles. The temperature I need to measure is the the range of 1000+ degrees celcius and this is the only option i have according to microchip reference.

My question is how do i read the signal or is my board faulty.

Thank you.

2

Do you have a data sheet for the thermopiles you are using?

sim

3

Maybe the voltage is too low.
Do you get any reading (AD1 or AD2) when you run the K8055_Demo.exe?

4

I am using the velleman thermister as the reference and a regular K type thermocouple.

I have not bought the thermister yet and the thermocouple does not show any reading even on the demo software. I went and bought another thermocouple and I got the same problem.

If the voltage is really too low, may I know how do I fix the problem? A different board?

Thank you.

5

K types put out 41 µV/°C
(ref. picotech.com/applications/thermocouple.html).

So you’ll need something in the range of 50~100x amplification.
Try 100 Ohms for R8 & R9.
The input impedance of the K8055 is low (1500 Ohms) compared to dedicated readers (typically 1~10MOhm). Accuracy will suffer, but you should still be able to get it to work.

sim