PCI 6033 Analog measurement noise

[auerdoan]

I want to make sure I'm doing all I can to get the best measurement possible

Im using a SCB 100; I'm using a PCI 6033 card.

I've connected my analog wires

Looking at a chart labeled I/O connector for 64 channel E series Devices..

I see for ground a choice AI GND, AI SENSE, AI SENSE 2, EXT REF, AO GND, D GND.

I used the AI GND.

my measurement is close but there is some noise 4.30 milliamp is expected I'm getting 4.80 on some units 

in Measurement and Automation I've set it up for ref single ended and a -10 to 10 vdc measurement

I connected a wire from the AI GND to my units I measure power supply ground the wire is short less than 10 inches, 16 gauge.

Am I using the correct ground?.

Thanks-Kurt

[Broken_Arrow]

That ground is fine. What I don't understand is: You set it up for a -10 to 10 vdc measurement, yet you are measuring Current?

[aeastet]

The best way to make sure that you are getting the best signal possible is to isolate your signal to the DAQ system. I would also use a differentail signal. Make sure you are using sheilded cables if there is any AC or noise generating signal close. You do need to get your signal correct going into the system first as the post above states. If you are measureing current you will have to place a resistor between the positive and negitive terminal depending on how you set up your signal. I would again highly recommend differential signal for less noise.

[Broken_Arrow]

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aeastet wrote:

I would again highly recommend differential signal for less noise.

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Kudos!

[johnsold]

Kurt,

You describe the expected signal as 4.30 and the measured result as 4.80.  You also asked about noise.  Noise can be broadly defined as anything unwanted in your measurement, but specifically defining the nature of the error is more useful.

Several other possibilities occur to me: Gain error, offset, common mode current, ...

What is the frequency range of the desired signal?  Does the measured result have the same frequency distribution?  Do all channels exhibit the same type of erroneous behavior?  Does the error correlate with anything else in the system (worse when the heater is energized for example)?  What are the dynamic range and the source impedance of the desired signal? Are the signal sources grounded or floating?  How are the inputs of unused channels connected?

Lynn 

[auerdoan · Accepted solution]

Ok, sorry i haven't been able to post my results.

ive been busy fixing my system.

It turned out to be a wiring issue stemmed from my point of measurement

my ground reference was riding with the units power supply ground and should of been running isolated to my ground strip.

The previous way the wire was acting like a resister.

Thanks