TC-08 USB Isolation

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nconrad
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TC-08 USB Isolation

Post by nconrad » Sun Jan 21, 2018 8:32 pm

Hi,

In our application, we'd like isolation between the TC-08's ground and our thermocouples.

Does the TC-08 provide any sort of isolation already? I noticed that its USB connector's color is orange, and I was wondering if that implied that it was isolated?

Thanks,

Nathan

Gerry
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Re: TC-08 USB Isolation

Post by Gerry » Mon Jan 22, 2018 3:33 pm

Hi Nathan,

The USB connector on the TC-08 is just a standard USB connector (the colour has no significance regarding the USB implemented inside the TC-08). So, the TC-08 doesn't have isolated grounds at the input.

I'm assuming that you'd like to perform the temperature measurement with the Thermocouple in contact with the surface that needs to be measured (which is why you need the isolation) in which case, could you tell us exactly what you will be logging the temperature of, and what temperature you will be measuring to.

Regards,

Gerry
Gerry
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nconrad
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Re: TC-08 USB Isolation

Post by nconrad » Mon Jan 22, 2018 7:39 pm

Thanks for the reply.

We're measuring temperatures between 10 and 55 C. The thermocouple will hopefully not come in contact with a signal, but it's possible that it will (on accident).

The thermocouple will be wired along the path following wiring with a RF signal (60 Vpeak), and we've demonstrated good rejection of that signal with the TC-08 logger. Mechanical damage could cause these wires to short. I'm planning on buying a USB isolator in order to remove the risk of damage to the TC-08.

I'd rather use a RTD, but due to size/mechanical restrictions our mechanical engineering folks prefer thermocouples.

We actually only need a single thermocouple channel, but due to good results with the TC-08, we'd like to continue using it.
Last edited by nconrad on Thu Feb 15, 2018 1:57 am, edited 1 time in total.

nconrad
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Re: TC-08 USB Isolation

Post by nconrad » Mon Jan 22, 2018 7:53 pm

I forgot to mention that it's also possible that our thermocouple will come in contact with salt water or conductive gels, but those are hopefully close to ground potential so it would be more of a measurement accuracy concern than a equipment damage concern. I believe our previous testing was done using a laptop, running on battery power (isolated).

Gerry
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Re: TC-08 USB Isolation

Post by Gerry » Wed Jan 24, 2018 3:48 pm

Hi Nathan,

OK, an isolator would be the way to go then, and you will obviously need one that breaks ground loops. Fortunately, you would be able to use a Full-Speed USB 2.0 isolator Like this one (http://cds.linear.com/docs/en/product-s ... d/2884.pdf) (High-Speed USB isolators that work with our High-Speed data acquisition products are harder to find).

As an aside, I would also check the potential corrosion due to salt water, based upon the alloy used for the thermocouple type.

Regards,

Gerry
Gerry
Technical Specialist

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