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TC08 - tc08_set_channel slope and offset values

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TC08 - tc08_set_channel slope and offset values

Postby Goran » Wed Mar 17, 2004 12:36 pm

Hello!

I am using TC-08 from Excel. The measurements are working fine but now I want to use tc08_set_channel function to change the slope and offset to calibrate the sensor. I have checked the TC-08 Manual V1.0 where tc08_set_channel function is described but I found no details on offset and slope. I did some tests and I think that the offset has to be entered in 1/100 degree Celsius but I am not sure. And I have no idea how to use the slope.

Any help is more then welcome.

Best regards,
Goran Vukusic

Tecan Austria GmbH
Goran
 

TC08 - tc08_set_channel slope and offset values

Postby Goran » Wed Mar 17, 2004 1:21 pm

Hello again,

in the meantime I have found a description for Offset:

The scale of the offset parameter depends on the type of thermocouple, but is typically about 0.02 degrees. The gain adjusts are added onto the gain, so zero gives the default gain. +1 gives a gain adjustment of +0.01%. The maximum gain adjust is about ±1%. Note that the slope and offset have no effect when using type X (60mV input).

But slope description was not that good, stating only that one should "adjust the slope for the channel until the channel temperature reading is correct".

I am using type K thermocouple, and a sample on how to do the calibration would help me a lot.

Best regards,
Goran Vukusic
Goran
 

Postby markspencer » Thu Mar 18, 2004 10:19 am

Hi,

The offset is to calibrate temperature between 0-100 degrees C. This is done by adjusting the temperature for each channel and bring it into line with the cold junction.

One method of achieveing this would be by using a loop and starting the offset value as 0, then compare the channels temperature with the coldjuction. If the channels temperature is below the cold junction you would increase the offset value, or the if the cold junction is above the channel temperature then you would decrease the offset value. This would keep repeating until the channel temperature get as close to the cold junction as possible. You might never get the temperature and cold junction to be exactly the same.

The gain is calculated by using a thermocouple at a known temperature, ideallly this would be a thermocouple simulator, then using the % values the process is repeated by increasing the value upwards or downwards as required. When it says opposite end of range, if you are measuring 0-100 degrees C, then the thermocouple should be at 100 degrees C.

I hope this helps.

Best regards,
Regards,

Mark Spencer
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