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Topic: A lot of errors with two thermocouples (Read 4074 times) previous topic - next topic

ElCaron

@riva
Yes, I have. Also, the problem already starts when I just connect a second element in addition to the first one.

@robtillaart
Still unlikely with 1.5mA. But Ill test it. I will also have a look which line exactly causes the malfunction.

Riva


@riva
Yes, I have. Also, the problem already starts when I just connect a second element in addition to the first one.

What if you use pulldown resistors on the MOSI, CS & CLK buses?

ElCaron

#17
Jan 01, 2014, 03:53 pm Last Edit: Jan 01, 2014, 03:55 pm by ElCaron Reason: 1
I think I found the problem. I tried to power the second amplifier from a breadboard power supply with common ground with the Arduino. Then I wanted to see if the DO or CLK line causes the errors. What I found was, that only connecting the power pins, even from another supply, where enough to trigger the problem. So what I found was that the housings of the two thermocouples were electrically connected via an aluminium tube for ventilation - though I have to admit that I didn't know they were not allowed to.
No, after I isolated one of the couples and made sure that not even the braided metal covers of the cables touch, the isolated one works properly. The other one, which goes into the metal exhaust pipe, still gives errors about every second reading. I can live with that, if I have to.

@Riva:
The communication seems to work fine, since I can always read the internal temperature.

robtillaart

Grounds of the different power supplies and the Arduino should be connected to create a common ground
(= reference for all signals)
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

ElCaron

Thanks, I have done that. It is also in my last posting ;)

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