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USB TC-08 measurement accuracy, isolation, update rate

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USB TC-08 measurement accuracy, isolation, update rate

Postby philthy » Wed Dec 08, 2004 5:04 pm

Your web page information for the USB TC-08 quotes temperature accuracy; " Sum of ±0.2% of reading and ±0.5 °C "

1) Does this include the cold junction compensation error ? (is this the ±0.5°C?)

2) what is the definition here of the zero & span "of reading" ?

eg if the reading is 300°C on a k-type thermocouple, is the accuracy;
based on the zero of the k-type range, i.e. 0.2% * (-270 to 300°C) + 0.5°C = 1.64°C
or is it based on a 0°C reference junction 0.2% * (0 to 300°C) + 0.5°C = 1.1°C
or is it based on actual mV input ? (i.e. still zeroed on 0°C reference junction, but not linear with temperature.)


3) are the channels isolated from each other, or would I need to use isolated thermocouples to avoid ground loops ?


4) Update rate is listed as 100ms per channel. Is this a characteristic of the TC-08, or the bus/Picolog software? I need one reading with rapid update, some others which update time doesn't matter. So if I put the single reading into one TC-08, and the others into a second TC-08, both into a single PC/Picolog session, will I get 100ms sample rate on the first reading?
philthy
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Joined: Wed Dec 08, 2004 4:05 pm
Location: UK

Postby Sarah » Wed Dec 15, 2004 11:35 am

Hi

Thank you for your post.

1) Yes the 0.5C is the CJC possible error.

2) The ±0.2% is relative to zero, so for 300C the accuracy would be 1.1C. You also need to take into account the accuracy of individual thermocouples.

3) The channels are not isolated so you may wish to use isolated thermocouples.

4) The 100ms sample rate is a specification of the hardware, this is the fastest the unit itself can sample. Therefore if you use 2 channels on 2 seperate units this will be quicker than using 2 channels on the same unit.

Hope this helps

Best Regards
Sarah
 


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