We currently use TC-08 for temperature and voltage measuring. Channel 1-6 are for thermocouples inputs while channel 7-8 are for voltage measuring (0-5V). We got two TC-08 Single-Channel Terminal Boards to convert the voltage. (switch set to OFF).
The problem is that when we try to measure the voltages from a circuit, the readings of all channels get crazy. Seems that the introduction of voltages interfere the whole system. The circuit is powered by a power supply and the TC-08 is connected to a laptop with power plugged. They are connected to the same power outlet.
BTW, if we try to measure the voltage of a AA battery, the readings seem good.
Could you please provide us some ideas to solve this problem? Thanks
Try with the laptop running on it's battery, and if this doesn't fix things then try to make sure that there is a common ground between your circuit and the laptop, plugging into the same power outlet may not be sufficient.
What are the thermocouples connected to and measuring ?
Battywoo: did it fix your problem? I have the same issue. If i put in the single channel terminal board and measure voltage (0-5V) the thermocouple readings go crazy. If I then connect the terminal board to ground the thermocouples are good but the voltage measurement is wrong (more than if not grounded). Can also this be a problem of having different earthing locations for the computer and the terminal boards?
Previously I solved this by having only one terminal board per TC08 logger, but it is an expensive solution.
I have tried that but it doesn't help. Below is the result of some of the measurements I did when trying to fix this. I will look into this more tomorrow, and it would be great with some advice.
With no earthing I get the following readings when both terminal boards are insterted in the logger:
condensing: 11,9 mV
evaporating: 4,76 mV
with only the condensing inserted:
condensing: 10,5 mV
with only evaporating inserted:
evaporating: 4,22 mV
only condensing with earting of the terminal
condensing: 24mV
Please ensure that the voltages being input to the TC-08 after the scale-down by the resistors does not exceed the Common Mode voltage range (+/- 7.5V).
If you could provide a diagram or photograph showing the connections to the terminal board and where they connect to, that might be helpful.