Help wiring a pressure transducer

[justinvandenbosch]

My transducers are only 3 wires though.  only has a positive signal going out, the negative is supposed to be just the ground, which common for the entire DAQ, is it not?  So do I jump a ground terminal in the DAQ to AI8 (pin 2)?   How do I know which AI terminals I should be using?  How do you decide on AI1 and AI8?  should I just be using pins in sequence? (ie, pin 1 and pin 2 for the first transducer)

I figured I have it wired wrong since it is giving the characteristics of a floating device with no ground. 

[johnsold]

With a 3-wire transducer you can use the single ended input mode, not differential. Connect the supply or excitation wires of both transducers to +5 V. Connect the Return, Common, or Ground (whatever they call them) wires to ground. Connect the signal wires to AI0 and AI1.  If you are using an external power source for the excitation, connect its ground to AI GND also.

Lynn

[J-Kane]

Yes, that is the problem, yoiu are using a diff not a single ended A/D.  Your pins are marked AI 0, AI 8, AI GND for pins 1, 2, AND 3.  If you were using this as a singal ended input, your postive would go to pin1  (AI 0) and the neg to pin 3 (AI GND).  You would attach input #8 to pins 2 and 3  (AI 😎 (AI GRD).  But since this a diff input youi connect the two output wires from the tranducer to pins 1 AND 2.

With a three wire tranducer youi would connect the 5 volt transducer line to the 5 volt supply on the board, pin #47.  The signal wire from the tranducer would be connected to the input for the first channal (# 0) pin 1.  The ground wire from the tranducer is ground for both the power and the signal.  So this wire is connected to both pin #63 and pin #2. The second tranducer would be connected to pins #47, 63, #4 and #5.

I think I have this right.  If yoiu have any questions or don't understand this, write back.  I am very tired now and am headed to bet.  I will write back Friday.

Good luck,

John

[justinvandenbosch]

Hi John, Thank you for the concise instructions!  I hooked it up like you said but I had a slight problem, my RSE option in my software is greyed out.  So I jumped the AI SENSE pin (13) to the AI GND pin (29) and used NRSE and this is finally giving the results I'm expecting.  Is there a better way of doing this?  Why is this option greyed out? I know RSE isn't supported in 6013 and 6014 but there is no mention of 6015 not supporting RSE.

Is there a software option that needs to be changed?  I am still getting some noise (obviously I'm expecting some) but can this be reduced by using an option other than jumping pin 13 to 29?

Thanks again for your help everyone!

[J-Kane]

i don't know about yoiur first question (RSE, AI sense, AI GND) yet,  But I do have a suggestion about the second question.

We do a lot of gtrain gauges and get noise.  This will depend on how fast your board is and how fast youi must take the data.  But what we do is to do some averaging of the input data.  We will take in N readings they devide their total by N ande put that number out as one data point.  As an example we will often take readings at 1 per sec.  So we have a loop that after puting out one reading will wait for one second before taking the next reading.  In side the loop we will take 10 readings, find their average and put that average out as the reading for that second.

Hope this helps