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Channels showing "open circuit" on TC-08

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Channels showing "open circuit" on TC-08

Postby Guest » Mon Mar 17, 2008 9:52 am

Hi,
I am currently running a TC-08 through a USB connection, I have all 8 channels logging but sometimes have only 4 channels connected to type k thermocouples whilst the other 4 are not connected ie open circuit.

I would expect the 4 that are not connected to show a open circuit high value or **** however this does not happen and what is shown is roughly an ambient temperature. Also when i unplug one of the connected thermocouples the temperature shown on this channel also reverts to this previously stated "ambient temperature"

This obviously causes problems in such that if a thermocouple breaks i expect the upscale alarm to trigger and this will obviously not happen if only ambient is displayed on an "open circuit condition".

I have checked all of the settings and cannot see where this problem can be rectified and I have also replaced the TC-08 with another unit but the same problem occurs.

Any help you can give me would be greatly appreciated
Guest
 

Postby ziko » Mon Mar 17, 2008 3:52 pm

Hi that is how it works.

This is because each channel would be meausring the cold junction temperature and the noise. Why do you need to activate the other channels that you are not using?

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Ziko

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Postby Guest » Wed Mar 19, 2008 8:47 am

If this is how it works, it is very strange and not like all other logging software ie LABVIEW, SPECVIEW, YOKOGOWA, EUROTHERM. When a thermocouple is either not plugged into a socket or has developed a fault the system should enter a short circuit condition and go upscale, if the logger goes to ambient condition when a fault occurs on a thermocouple how can you possibly tell that the thermocouple has broken? This would be especially confusing if the normal measured temperature was at around ambient as you would think the thermocouple was working normally.

Maybe there has been a misunderstanding so i will further explain the application in which the unit is being used.

The unit is being used in a laboratory situation to monitor the temperatures of oils that are being "dripped" onto a heated bar of metal, as the oils move down the bar they are cooling so the range of temperatures is between 200°C and ambient. There are 4 permanent thermocouples affixed to the bar at different positions along it and 4 "floating" thermocouples that can be fixed at any time the tester wishes to monitor any other particular temperature (this is why all 8 channels need to be logged but sometimes only 4 are used). The testing is such that it is imperitive that if there is a fault with a thermocouple it is replaced asap, the bar itself vibrates so thermocouple fracture can and does occur.

Perhaps this will help you to understand why going to an ambient condition under fault conditions is such a problem and in 20 years it is the first time i have personally seen it.

Thank you for your help.
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Postby ziko » Fri Mar 28, 2008 11:05 am

Hi, sorry that the product does not meet your requirements on this occasion.

Kind regards
Ziko

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