Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

USB 6009 and AD595 connection to read thermocouple output

Hi,

 

I am trying to use USB 6009 to read thermocouple output in LabVIEW with AD595 as the amplifier. The problem is that I always get a voltage output of around 320 mV even if I heat the thermocouple. Maybe the output voltage changes slightly and I can't tell them visually, but it is absolutely not something like 10 mV/C.

 

The connection is based on the following figure. Pin 11 is connected to the 5 V supply of USB 6009. Pins 1, 4, 7, 13 are connected to the ground. Pins 8 and 9 are connected to AI0+ and another wire leads pins 1, 4, 7, 13 to AI0-. May I have some suggestions where I am wrong?

HarryZhu_0-1635258899172.png

 

Many thanks,

Harry

 

0 Kudos
Message 1 of 4
(1,190 Views)

You can ignore the AI0- and use the Analog Input in single-ended mode as your signal is also single-ended.

 

Now your connection will be just the Pin 8,9 to AI and you configure your DAQmx task to be RSE.

 

To ensure that your AD595 is working properly, power up the circuit and measure the voltage at Pin8, 9 using a handheld DMM.

 

BTW, I don't think you should connect Pin 1 to GND

Santhosh
Soliton Technologies

New to the forum? Please read community guidelines and how to ask smart questions

Only two ways to appreciate someone who spent their free time to reply/answer your question - give them Kudos or mark their reply as the answer/solution.

Finding it hard to source NI hardware? Try NI Trading Post
Message 2 of 4
(1,165 Views)

Hi Santhosh,

 

Many thanks for your reply! I have tried it with your suggestion. It works perfectly! The only thing I didn't follow is that I still keep pin 1 connected to the ground.

 

When I disconnect pin 1 from the ground, the signals look like this:

HarryZhu_0-1635423749359.png

But when I connect to the ground, the signals look better like this:

HarryZhu_1-1635423896930.png

 

So I think this may be a better option. I also use a pull-down resistor to make it possible to measure lower temperatures.

 

Thank you very much for your help!

 

Best regards from UK,

Harry

0 Kudos
Message 3 of 4
(1,133 Views)

Hi Harry

Are you sure that you want to use type K thermocouples in your application ? Unless cost is the overrideing consideration, you will get better stability from other types, e.g. N. 

 

Obviously connecting pin 1 to common means that your thermocouple wires and junction have to be electrically isolated from the point where you want to measure temperature; this will introduce a responce lag.

 

Have you considered using a signal conditioning module? These can do all the hard work for you, and provide signal isolation. e.g. https://www.dataq.com/products/di-5b/di-5b47/di5b47n-15.html 

0 Kudos
Message 4 of 4
(1,108 Views)