Bad temp readings with MAX31855 breakout board
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- scott216
- Posts: 163
- Joined: Sun Apr 12, 2009 11:08 am
Bad temp readings with MAX31855 breakout board
I have four MAX31855 breakout boards connected to an arduino mega. They breakout boards are close to the thermocouples. Three of the thermocouples have a 5-conductor 18 gauges wire connecting the breakout board to my arduino mega. This 5 conductor wire is about 10 feet long. The fourth breakout board is right next to the arduino. I have the little capacitor soldered to the t/c terminal block. The actual temperature for all the thermocouples is room temp, high 60s low 70s. But they are all reading in the low 30s. The temperature jumps around a lot and it's frequently exactly 32 degrees. Anyone have some suggestions to what might be causing this?
- adafruit_support_bill
- Posts: 88089
- Joined: Sat Feb 07, 2009 10:11 am
Re: Bad temp readings with MAX31855 breakout board
You can't extend thermocouples with copper wire. They must be connected directly to the amplifiers, or extended with type K thermocouple extension wire.
- scott216
- Posts: 163
- Joined: Sun Apr 12, 2009 11:08 am
Re: Bad temp readings with MAX31855 breakout board
I'm not extending the thermocouple wires. The thermocouples are wired directly into the breakout board. On the other side of the breakout board I soldered in at 6-position terminal block. I have a 5-conductor cable connected to this terminal block (I didn't connect anything to 3v pin). 10 feet away, the other side of the 5-conductor cable goes to a terminal block that's connected to my Arduino mega.adafruit_support wrote:You can't extend thermocouples with copper wire. They must be connected directly to the amplifiers, or extended with type K thermocouple extension wire.
- adafruit_support_bill
- Posts: 88089
- Joined: Sat Feb 07, 2009 10:11 am
Re: Bad temp readings with MAX31855 breakout board
10 feet is rather long. But if you are seeing the same results from the closer one that is not likely the problem.
What does the internal temperature report?
What does the internal temperature report?
Code: Select all
// basic readout test, just print the current temp
Serial.print("Internal Temp = ");
Serial.println(thermocouple.readInternal());
- scott216
- Posts: 163
- Joined: Sun Apr 12, 2009 11:08 am
Re: Bad temp readings with MAX31855 breakout board
I won't be able to test that until this weekend. Any additional things you suggest I test while I'm at it?
- adafruit_support_bill
- Posts: 88089
- Joined: Sat Feb 07, 2009 10:11 am
Re: Bad temp readings with MAX31855 breakout board
Make sure that the thermocouple wires are firmly clamped in the screw-terminals. Keep the probes away from any potential EMI sources.Any additional things you suggest I test while I'm at it?
Observe the change in output with changes in temperature. (cold/hot water are easy ways to test this). If the response is in the wrong direction, reverse the probe leads. We did have a bunch of them that were marked in reverse of the normal color codes.
Please be positive and constructive with your questions and comments.