Themocouple problem

 
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Guest
PostPosted: Fri Feb 28, 2003 1:58 pm    Post subject: Themocouple problem Reply with quote
Hi All,

I have a very strange problem with a K-type Thermocouple. Confused

The thermocouple is connected to a "Comark Microprocessor thermometer" which outputs a 1V range analogue signal to an ADC-16.

The problem is that when the temperature reaches and passes a multiple of 100C it drops the hundred value. i.e. 20C = 20C, 60C = 60C, 120C = 20C, 240C = 40C. The value is reported like this on both the screen and in the data file.

The value range is set -270C to 1370C, and the field is set to 9 digits with 3 decimal places.

Has anybody got any idea as to what is happening ?
And especially how to correct it ? Rolling Eyes
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Alan
Guest
PostPosted: Wed Mar 05, 2003 8:05 pm    Post subject: Thermocouple problem Reply with quote
Hi,

I guess the first step is to see if the problem is due to the comark thermometer autoranging or some problem with the setup of the ADC16. The best way to do this would be to monitor the output to the ADC16 with a voltmeter and check it tracks smoothly with temperature.

Assuming it does, the problem is likely to be with the scaling used in PicoScope to convert from volts to temperature. Please can you let us know what scaling method & settings you are using.

Another solution would be to ditch the comark product and use a Pico TC08 for the thermocouple measurement Very Happy

Regards
Alan
Pico
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