CONVERT VOLTAGE TO TEMPERATURE

[henryxrisdeb2050]

Hello, engineers.

I hope everything is fine. I am Henry Christian and am working on the project of cooling and heating by using thermocouples and peltier modules. Is there someone who has used the NI 6009 data acquisition card before? I want to know the mathematical function that can be used to convert the voltage to the temperature as I can plot the curve of the real temperature vs time or other output behavior. So if there is someone who did the closed-loop control of this kind of control, he/she can let me know. Maybe I can get some ideas. The attached picture was the simulation schematic to acquire temperature from the external electronic circuit. I added an offset and gain, but the output is not well controlled in the way of characterization.

If there is someone who can help me, I would appreciate it.

[GerdW]

Hi Henry,

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@henryxrisdeb2050 wrote:

I am Henry Christian and am working on the project of cooling and heating by using thermocouples and peltier modules. Is there someone who has used the NI 6009 data acquisition card before? I want to know the mathematical function that can be used to convert the voltage to the temperature as I can plot the curve of the real temperature vs time or other output behavior. So if there is someone who did the closed-loop control of this kind of control, he/she can let me know. 

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That NI6009 is old, very old. And it is not suited for thermocouples!

I recommend to use some amplifiers for those thermocouples - or a different DAQ card at all…

The "math function" can be found in the datasheets of your thermocouples. Or at Wikipedia and other websites showing big tables for each kind of thermocouple… (LabVIEW comes with a ready-to-use conversion function for most common thermocouple types.)

A closed-loop control using thermocouples and peltier elements doesn't sound too hard: what are your requirements?

Btw.: I guess you want to use LabVIEW (+DAQmx) when you ask your question in a LabVIEW board, don't you?

[NIquist]

Since you are using an NI DAQ you can just use the NI DAQmx driver and select temperature measurement with thermocouples.  It will show you how to connect, you can tell it what type of thermocouple, whether you are using cold-junction compensation etc. etc.  It's all built-in to the DAQmx package.

Here is the Getting Started page:  Connecting Thermocouple Signals to a DAQ Device - National Instruments (ni.com)

There is a LOT more info available with a quick search, checking your manuals and perusing the Example Finder for DAQmx > Temperature > thermocouples.  It's a good idea to start with an official example and modify to your needs.

[henryxrisdeb2050]

Hello, engineers.

I hope everything is fine. I am Henry Christian and am working on the project of cooling and heating by using thermocouples and Peltier modules. Is there someone who has used the NI 6009 data acquisition card before?

So I want to do the heating by changing the voltage of the analog output of the NI 6009 from 0-5V for increasing or decreasing the power of the Peltier module but it is still challenging, because if I change the analog output voltage of the NI card, it works from zero to one (only zero and one), and my purpose is to change from 0-5V. I don't know the reason behind this error because if I change to the other values, except zero and one, I get the mistake in SAOSSB S-Function (made by Matlab itself) for the DAQ Analog Output (Single Scan) block and the screenshot is attached here.

If there is someone who can help me, I would appreciate it.

ERROR

[GerdW]

Hi Henry,

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@henryxrisdeb2050 wrote:

Is there someone who has used the NI 6009 data acquisition card before?

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As already said: the NI6009 is very old stuff, so lots of people used it before you.

Most of them used LabVIEW with DAQmx, so you should explicitely mention if you don't use both but other programming environments…

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@henryxrisdeb2050 wrote:

So I want to do the heating by changing the voltage of the analog output of the NI 6009 from 0-5V for increasing or decreasing the power of the Peltier module but it is still challenging, because if I change the analog output voltage of the NI card, it works from zero to one (only zero and one), and my purpose is to change from 0-5V. I don't know the reason behind this error because if I change to the other values, except zero and one, I get the mistake in SAOSSB S-Function (made by Matlab itself) for the DAQ Analog Output (Single Scan) block and the screenshot is attached here.

ERROR

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First of all: we talk about LabVIEW and not MATLAB/Simulink in a LabVIEW forum…

And we don't have your Simulink environment nor your MATLAB functions!

The error seems to indicate your Matlab function expects to handle a digital output channel and so it wants to receive the values 0/1 exclusively. Your application requires to use an analog output channel…

(I hope you use some amplifier to drive your Peltier element from that NI6009 AO pin…)

[henryxrisdeb2050]

yes I use gains,filters, and amplifiers to drive your Peltier element from that NI6009   pin AO.0 and AO.1