Thermocouple wiring with a Voltage Divider
Hello,
I am trying to measure the temperature through a K-type thermocouple by making a voltage divider connection. As you can see in the picture attached, I am wiring a resistor ( 10 kOhm) with the pins of the thermocouple to the DAQ (NI-6009).
The problem that I am facing is when running this with LabVIEW. I am attaching a file I created in order to control a heating element depending upon the temperature measurement. The result I get is -360.425 C which totally makes no sense, and makes me wonder what is wrong with either the .vi file or the wiring (I have checked the polarity of both the resistor and the thermocouple and that part should be solved already).
I am attaching a picture of the result since to obtain something everything needs to be wired first.
Thanks in advance
JL
Attachments:
Result.png 44 KB
2013-07-01 17.37.57.jpg 2125 KB
OnOffFullPower.vi 107 KB
It is hard to see how you have the voltage divider connected in the picture. Can you post an image of the schematic?
I never heard of anyone uisng a voltage divider on the output of a thermocouple. The voltage is quite small and dividing it makes little sense.
Next, the USB-6009 is marginally useful for measuring the output of a thermocouple. The resolution is about 1 degree.
Your formula for converting voltage to temperature is suspect. I do not have any hardware so I just generated an array of values from zero to 0.05. This results in temperatures on the chart of -97 to -87 degrees. For a Type K thermocouple 0 to 50 mV should represent temperatures from 0 to 1232 C.
Lynn
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