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I know about changing resolution as I'm using thermocouples. The problem is that the temperature readings jump around by up to 5 degrees. I'm using differential mode with the Mux80 and Daqfactory. Resolution index 9 (U6pro). I gounded the negative channels with a 10K resistor. I'm measuring the temperature of water inside electric water urns using type K thermocouples. The readings are fine when the units are unplugged, but as soon as I plug them in, the reading starts jumping around. Sometimes when the units are turned on the reading varies even more. It seems like a ground loop issue. I insulated the thermocouple ends with 'glue type' heat shrink tubing. (Maybe the glue has a low resistance?) Usind a higher resolution index gives better results so I switched to resolution index 10. But the reading still jump around a little. I tried using 10M resitors to ground (as well as no gnd connection at all) but the jumping around increased even more. I want to eventualy add much more channels and that would be a problem with such a high resolution index.
I have a 'feeling' than increasing the settling factor might give a more stable reading.
I do not have multiple thermocouples in the same cup of water.
The readings do stabilize when the thermocouples are removed from the water.
I'm using thermocouples because they are cheaper, more versatile, can fit into small spaces, able to measure higher temperatures etc... (I have silicon sensors too - LM34CAZ)
Meanwhile, I'm using a higher resolution on the labjack - resolution index 10 - readings are a little more stable.
You said the readings stabilized when the thermocouples are removed from the water. Can you do some experiments to try to see if the problem is actually related to contact with the water, or just related to how close the thermocouple is to the electrically active circuitry of the urn?
If you only have 1 thermocouple connected (no other connections except USB), can you still cause the problems, or only with multiple thermocouples.
If you can cause the problem with just 1 thermocouple, you could add a USB isolator and see if the problem goes away:
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See the example "AIN Configuration U6.ctl":
https://labjack.com/support/software/examples/ud/daqfactory
It does not actually configure settling, but it does resolution which is a similar device-wide parameter:
https://labjack.com/support/datasheets/u6/high-level-driver/example-pseu...
Wow. That was a quick response. Thanks.
I know about changing resolution as I'm using thermocouples. The problem is that the temperature readings jump around by up to 5 degrees. I'm using differential mode with the Mux80 and Daqfactory. Resolution index 9 (U6pro). I gounded the negative channels with a 10K resistor. I'm measuring the temperature of water inside electric water urns using type K thermocouples. The readings are fine when the units are unplugged, but as soon as I plug them in, the reading starts jumping around. Sometimes when the units are turned on the reading varies even more. It seems like a ground loop issue. I insulated the thermocouple ends with 'glue type' heat shrink tubing. (Maybe the glue has a low resistance?) Usind a higher resolution index gives better results so I switched to resolution index 10. But the reading still jump around a little. I tried using 10M resitors to ground (as well as no gnd connection at all) but the jumping around increased even more. I want to eventualy add much more channels and that would be a problem with such a high resolution index.
I have a 'feeling' than increasing the settling factor might give a more stable reading.
Any comments?
Thanks
Nope.... Changing the settling factor doesn't seem to have any effect.
Are multiple thermocouples in the same pool of water?
If you take some or perhaps all of the thermocouples out of the water do they then work fine, even with the urns on?
Any particular reason you are using thermocouples? You can often use silicon type sensors at water temperatures:
https://labjack.com/support/app-notes/temperature-sensors
I do not have multiple thermocouples in the same cup of water.
The readings do stabilize when the thermocouples are removed from the water.
I'm using thermocouples because they are cheaper, more versatile, can fit into small spaces, able to measure higher temperatures etc... (I have silicon sensors too - LM34CAZ)
Meanwhile, I'm using a higher resolution on the labjack - resolution index 10 - readings are a little more stable.
You said the readings stabilized when the thermocouples are removed from the water. Can you do some experiments to try to see if the problem is actually related to contact with the water, or just related to how close the thermocouple is to the electrically active circuitry of the urn?
If you only have 1 thermocouple connected (no other connections except USB), can you still cause the problems, or only with multiple thermocouples.
If you can cause the problem with just 1 thermocouple, you could add a USB isolator and see if the problem goes away:
http://microcontrollershop.com/product_info.php?currency=USD&products_id...
Thanks, Is that the isolator that you recommend? Do you recommend any other ones?
Any USB isolator should break the USB ground connection. That particular one is one we have and occasionaly use for something.
Do you know the current draw of the labjack U6 together with the Mux80?
The datasheets say about 100mA plus 5.5mA, so I would expect just over 100mA.
thanks