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PT-104 Differetial voltage readings

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PT-104 Differetial voltage readings

Postby gustavo » Tue Feb 05, 2013 2:16 pm

Hi there!

I am quite new using PT-104 and I bought it thinking to use it not only as a teperature logger but also as a differential voltage logger.

I developed a Wheatstone Bridge (a quarter bridge) to use strain gauges, supplied by 12v batteries and then, I developed a VB application to ave strain readings. In pico PT-104, I use the differencial voltage connections with V- (pin2), V+ (pin3) and about pin 4, wich corresponds to the ground, I have some issues...

First, I connected pin 4 to the + connection of the bidge's output and the readings doesn't became stable. The same thing happens when I connect - connection of the bridge's output witn pin 4.

With this information I ask:
1. Am I using the right type of connection in PT-104? What is the difference by using single-ended connection type?
2. I'm not quite familiarized with ground function in PT-104, How can I connect GRND in this scheme?

Thanks a lot for yout help!

Best Regards.

Gustavo
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Re: PT-104 Differetial voltage readings

Postby Martyn » Wed Feb 06, 2013 8:44 am

Pin 4 should be connected to the -ve of the battery feeding the bridge, however you must use a battery of around 4.5V otherwise you will be operating outside the range of the PT104.

The other part to check is that you are selecting the correct differential setting in your call to UsbPt104SetChannel, which should be USBPT104_DIFFERENTIAL_TO_2500MV
Martyn
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