Host Engineering Forum
General Category => General Discussion => Topic started by: MarkTTU on March 10, 2025, 08:21:27 PM
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I have a customer who has existing thermocouples installed and wires run where there's a single common negative wire for every 6 positive thermocouple wires. What I'd like to do is use three of the BX-08UT input cards where each captures 6 of the thermocouples. Can I just jumper the negative constantan wire from 0A to 1A, 2A, 3A, 4A, etc and then connect the individual copper wires to 1B, 2B, 3B, etc? Will that work?
Looking at the BX-08UT specs it appears that each of the analog inputs is internally independent so I'm not sure if jumping the commons will work or not.
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I have a customer who has existing thermocouples installed and wires run where there's a single common negative wire for every 6 positive thermocouple wires. What I'd like to do is use three of the BX-08UT input cards where each captures 6 of the thermocouples. Can I just jumper the negative constantan wire from 0A to 1A, 2A, 3A, 4A, etc and then connect the individual copper wires to 1B, 2B, 3B, etc? Will that work?
Looking at the BX-08UT specs it appears that each of the analog inputs is internally independent so I'm not sure if jumping the commons will work or not.
There is no need to jumper the A (-) terminals together at all; just land the (-) wire of each thermocouple. But if you do, the (-) of a T-type thermocouple is the constantan metal alloy. Therefore, it would be best to use constantan wire for the jumpers, or you will interfere with the built-in cold junction compensation.
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I have a customer who has existing thermocouples installed and wires run where there's a single common negative wire for every 6 positive thermocouple wires. What I'd like to do is use three of the BX-08UT input cards where each captures 6 of the thermocouples. Can I just jumper the negative constantan wire from 0A to 1A, 2A, 3A, 4A, etc and then connect the individual copper wires to 1B, 2B, 3B, etc? Will that work?
Looking at the BX-08UT specs it appears that each of the analog inputs is internally independent so I'm not sure if jumping the commons will work or not.
There is no need to jumper the A (-) terminals together at all; just land the (-) wire of each thermocouple. But if you do, the (-) of a T-type thermocouple is the constantan metal alloy. Therefore, it would be best to use constantan wire for the jumpers, or you will interfere with the built-in cold junction compensation.
The issue is I only have a single (-) wire for 6 separate (+) wires measuring temperature in 6 different locations. It's an existing setup where they ran a common (-) wire back to the control enclosure for all 6 temp readings.
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The issue is I only have a single (-) wire for 6 separate (+) wires measuring temperature in 6 different locations. It's an existing setup where they ran a common (-) wire back to the control enclosure for all 6 temp readings.
Then it's impossible to say what you'll get. Best thing is to just try it and see. The absolute value of the temp might be off if the single (-) wire is not constantan. Of course, the higher the temperature measurement you are doing, the less the cold junction compensation will have on the reading.
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It should work although it is really bad practice just to save a dime. It really isn't any different than doing takeoffs on a long wire run to check for breakage.