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TC-08 Ambient Temperature Error

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TC-08 Ambient Temperature Error

Postby JackMThompson » Fri May 04, 2012 4:19 pm

We're seeing a behavior that we're trying to make sense of. We are measuring temps using type J T/C probes in a coolant system, with the TC-08 logger in an air conditioned room. We were seeing odd shifts in measured temperatures as the room air conditioning system cycled on and off throughout the day. We ended up buying a styrofoam ice chest and put the TC-08 inside it to isolate it from the room and the temperature shifts went away. I find this odd that the ambient temp around the TC-08 would affect the readings, because doesn't the unit have cold junction compensation? Should we really have to do this to get accurate readings? Seems like something isn't right.

We are also seeing odd behavior when using thermocouple extensions, even though they are of the correct materials. When the mini connector (in between probe and TC-08) is subjected to changing ambient temps, we're also seeing shifts in the measured values. That doesn't seem to agree with the laws of intermediate metals I was taught in school, so that puzzles me as well.
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Re: TC-08 Ambient Temperature Error

Postby PeterF » Thu May 10, 2012 9:26 am

Hi,
The cold junction compensation in the TC-08 comprises a precision thermistor situated inside the case, in the area of the 8 input connectors. This attempts to measure the ambient temperature of the connectors. If the temperature is changing rapidly or the unit is in a draught, the thermistor may not be at the same temperature as the connectors, giving an error.
Are you sure that all the connectors and thermocouple wire are the same material as the thermocouple itself and the polarities are correct? The law of intermediate metals only applies if all the junctions are at the same temperature.
Please contact us again if you have any other questions.
Regards,
PeterF.
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Re: TC-08 Ambient Temperature Error

Postby Hanh » Wed Jul 11, 2012 12:45 am

Hi

i recently brought a TC-08-USB. It was working and have no problems. It was connected through PC and using type K thermal couples. Recently i am trying to measure temps of a LED light. The temperature readings were normal when the light was OFF. Since i turned ON the light, the temperature readings went off very high in range of 70-90 'C no matter at what ambient temps. What is wrong?

Regards,
Hanh
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Re: TC-08 Ambient Temperature Error

Postby Hitesh » Wed Jul 11, 2012 2:05 pm

Hi Hanh,

Are you getting incorrect values on all the channels?

How many channels are you using and which version of the PicoLog software is installed on your PC?

Are the thermocouples touching any metal surfaces?

Regards,
Hitesh

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Re: TC-08 Ambient Temperature Error

Postby Hanh » Wed Jul 11, 2012 3:56 pm

Hi

Yes i am getting incorrect reading on all the channels. It doesn't matter how many channels were using. i had have tried from one to all channels. it was the same getting incorrect reading. None of the thermocouples touching any metal surfaces. i am using the latest version R5.22.6 on W7 PC. Any suggestions.

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Hanh
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Re: TC-08 Ambient Temperature Error

Postby Hitesh » Wed Jul 11, 2012 4:58 pm

Hi,

It's worth checking if the LED is being driven via a mains transformer that it is at the same earthing ground as your PC.

If that doesn't help, please e-mail support@picotech.com referencing this forum post - you may need to return the unit for inspection.

If you have purchased the device from a distributor, you will need to return the device via them.

Thanks,
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