I have bought a MAX31855 thermocouple amplifier from Adafruit. I use it with RaspberryPi Zero W. But there are some problems.
1. It is not very stable. It often reads “nan”, and is very sensitive to what power supply is used
2. The input impedance appears not high enough. For example, for a thermocouple that is measured 0.75mv when it is not connected to the MAX31855 thermocouple amplifier, but reading becomes 0.45mv when connecting to the MAX31855.
I am not sure if my MAX31855 thermocouple amplifier is a bad one.
My question is that
1. Can I use the MAX31855 thermocouple amplifier with RaspberryPi Zero W.
2. Is there any limit on the length of thermocouple? My one is more than 10 meter.
Is it possible to wire 2 amplifiers to a single raspberry pi?
What is the fastest rate you can scan the Type K Thermocouple with the Raspberry Pi and Adafruit Amplifier?
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Thermocouples are very sensitive, requiring a good amplifier with a cold-compensation reference. The MAX31855K does everything for you, and can be easily interfaced with any microcontroller, even one without an analog input. This breakout board has the chip itself, a 3.3V regulator with 10uF bypass capacitors and level shifting circuitry, all assembled and tested. Comes with a 2 pin terminal block (for connecting to the thermocouple) and pin header (to plug into any breadboard or perfboard).
Your can Purchase a 1m K-type Thermocouple from ModMyPi Here!
Version 2.0 now includes ferrite beads and filter capacitor onboard for better stability, and has a a wider temperature measurement range!
The Adafruit Thermocouple Amplifier V2.0 Features:
- Compatible with both Raspberry Pi and Arduino
- Works with any K type thermocouple (Will NOT work with other types other than K)
- -200°C to +1350°C output in 0.25 degree increments
- Internal Temperature Reading
- 3.3 to 5v power supply and logic level compliant!
- SPI-controlled - SPI data output requires any 3 digital I/O pins.
- Includes ferrite beads and filter capacitor onboard for better stability
- Screw Terminal for Thermocouple Input