Hi to every one,
Is it possible to connect a thermocouple directly to the anolag ports of arduino? Output (thermocouple) is from 0 to 40mV.
Thanks in advance
Kenneth.
Assuming you could find a low enough reference voltage, maybe, but there's some other voodoo required for cold-temp compensation (since your thermocouple reads the temperature above ambient) and (some) non-linearity. At the very least, you'd need to use the 1.1V reference, which gives you 1.074mV steps for the 10bit ADC (considering your thermocouple is likely in the 50uV/c this is about 20 degrees/step). If you could find a 100 mV or 50mV reference you'd be in much better shape though (perhaps a forward biased diode with sufficient load current?).
A far better solution is a dedicated thermistor interface or amp though. Maxim and linear both make several (although they're not cheap, typically $5 to $15).
Another option is any of the pre-designed thermocouple compensation circuits. Most analog semiconductor manufacturers have some if you search their application notes, here's one from Maxim.
Ditto the Maxim device. It's got a reference, amplifier, ADC, and an SPI interface to talk to the Arduino.
I'm still trying to find a cheap t-couple jack, but I guess I'll have to break down and get some from Omega before I can proceed with my little project.
-j
Spiffed,
Well thanks
So an ampliflier is a must!
I'm limited to +12v & +5v so the Maxium MAX430 is out of question. Can someone please suggest an ampliflier circuit, maybe using the common 741 of simillar IC taking on account the supply voltage mentioned.
Thanks once again
Kenneth