Thermocouples K type display wrong readings when an AC component (heater) is connected to Solid State Relay Module

[tran88]

Could you please walk me the steps in electrical isolation? 

[tran88]

could you please walk me the steps for electrical isolation? should I do it on the AC heater, or the DC DAQ-6211 for thermocouples? 

[GerdW]

Hi tran,

when you don't know about electrical insulation then you should not work with an AC powered heater!

Ask the electrician responsible for your lab!

[tran88]

yes, unfortunately we do not have that kind of budget for something like that. 

However, I was reading more into the Solid State Relay Module, and it does have a optocouples which isolates AC current signal from being interfered with the DC signal. So, I do not think electrical isolation is the issue here. 

[RTSLVU]

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@tran88 wrote:

could you please walk me the steps for electrical isolation? should I do it on the AC heater, or the DC DAQ-6211 for thermocouples? 

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 I gave you the simplest solution, insulate your thermocouple. If it's being submerged in liquid then cover it heat shrink or something.

[RTSLVU]

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@tran88 wrote:

yes, unfortunately we do not have that kind of budget for something like that. 

However, I was reading more into the Solid State Relay Module, and it does have a optocouples which isolates AC current signal from being interfered with the DC signal. So, I do not think electrical isolation is the issue here. 

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Unfortunately, you also do not have the kind of knowledge necessary to do this safely.

It sounds like you have a heater submerged in liquid that is "leaking current" and basically electrifying the liquid itself. The leakage current is riding your thermocouple (it is just wire) in the form of a common mode voltage to your DAQ and causing your DAQ to read wrong.

[tran88]

unfortunately, it seem like you do not understand the whole problem here.

As I have many times and repeatedly mentioned above, the thermocouples are not submerged in the same liquid as the heater. Even the thermocouples that are measuring Air are being affected as soon as I turn on the heater. So, that leaking current and electrifying the liquid itself is not correct whatsoever. 

I am no electrical engineer, I have only asked one simple question, why is my Heater causing signal interference to my thermocouples, the thermocouples are connected to DAQ-6211? (even thou they are not measuring the temp of the liquid that the Heater is heating up).

Unless you have a solid answer and be nice in your response, and get your fact straight before responding something that does not make sense at all. PLEASE DO NOT RESPONSE TO MY QUESTION. 

[RTSLVU]

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@tran88 wrote:

unfortunately, it seem like you do not understand the whole problem here.

Unless you have a solid answer and be nice in your response, and get your fact straight before responding something that does not make sense at all. PLEASE DO NOT RESPONSE TO MY QUESTION. 

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I may not understand your problem but neither do you!

If powering up your heater is causing your DAQ to malfunction, you have a serious hardware issues in your test setup.

This it NOT a LabVIEW issue and neither I not nor anyone else on this board should even be trying to help you with this to begin with.

I am done, good luck.

[GerdW]

Hi Tran,

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@tran88 wrote:

unfortunately, it seem like you do not understand the whole problem here.

So, that leaking current … is not correct whatsoever. 

I am no electrical engineer,

Unless you have a solid answer and be nice in your response, and get your fact straight before responding something that does not make sense at all. PLEASE DO NOT RESPONSE TO MY QUESTION. 

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No need to yell at people giving you valid answers!

Something on my background:

I'm working in testbenches where we use different heat sources to heat up liquids (some of them flammable, like ethanol). Our electrical heaters are in the range of 30-150kW, and an additional heater using natural gas burners with upto 400kW.

We also use thermocouples to measure temperatures before, in and after those heaters, in the liquids and in the heaters.

We don't observe the problems you encounter.

We also have electricians being qualified to build and maintain those electrical devices. I am one of them as I have finished my apprenticeship in this area as well as I'm an electrical engineer with a university degree. As I'm working in Germany we also have rather strict rules and laws, to define who is allowed to work on such electric devices. Persons, which are allowed by their education, are called "trained persons".

We also have persons responsible for HSE (health, safety, environment) issues, also taking care of all work done in our testbenches.

With all that background I tell you: get an electrician who is a trained person to build up the electric components of your testbench. This way the test setup is no danger for your own health, and more importantly no danger for anybody else working with your setup!

tl;dr: Go and get a trained person to solve your testbench problems!

[pallen]

Sounds like a ground loop. 

If you're using a USB DAQ system, you need to isolate your PC's power supply or ensure your DAQ and TC amplifiers are completely isolated from the heater. 

You can buy a USB Isolator that will help with this situation.