Why voltage is so noisy through DAQ device although the value from multimeter is very stable?

[santo_13]

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@JonathanMATech wrote:

Could you recommend a LC lowpass circuit with component values that would perform as close as possible to a Fluke? I looked up the Fluke 115 datasheet but don't think they specify the circuit they use.

More information on how a Fluke is better than the NI USB-6002 would be great. Considering the original post of this thread, how does other NI hardware compare (though it would likely be out of our price range).

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Software filtering is recommended if you need the flexibility to adjust the performance. I would recommend sampling the AI at the highest rate possible, but in the software implement an averaging filter to reduce the sampling rate to just 4S/s (Fluke updates only at 4/s).

Please do consider the accuracy and resolution specification as it will vary compared to the Fluke DMM.

[Henrik_Volkers]

A handheld DMM is free floating,  a Lab Fluke DMM do a lot to isolate the inputs from powerline .. not done in that quality in a 6002, so additional noise is to be expected.

To provide better recommendations  please provide some more information:

What source are you measuring?

How is it connected? (to power, GND and 6002)

[JonathanMATech]

>A handheld DMM is free floating,  a Lab Fluke DMM do a lot to isolate the inputs from powerline .. not done in that quality in a 6002, so additional noise is to be expected.

I could disconnect the laptop from AC power for short term testing. If this would not be enough, please describe a circuit that would provide isolation.

>To provide better recommendations  please provide some more information:

>What source are you measuring?

>How is it connected? (to power, GND and 6002)

A generic DC voltage between 0 and 10 volts connected to the NI USB-6002's GND and ai7 pins.

If more information is needed, please, what is the exact information you are looking for? But I am trying to understand what the differences between a Fluke and NI USB-6002 generally.

[santo_13]

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@JonathanMATech wrote:

>A handheld DMM is free floating,  a Lab Fluke DMM do a lot to isolate the inputs from powerline .. not done in that quality in a 6002, so additional noise is to be expected.

I could disconnect the laptop from AC power for short term testing. If this would not be enough, please describe a circuit that would provide isolation.

>To provide better recommendations  please provide some more information:

>What source are you measuring?

>How is it connected? (to power, GND and 6002)

A generic DC voltage between 0 and 10 volts connected to the NI USB-6002's GND and ai7 pins.

If more information is needed, please, what is the exact information you are looking for? But I am trying to understand what the differences between a Fluke and NI USB-6002 generally.

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Essentially the electrical design is different between 6002 and Fluke DMM, this is analogous to the difference between a Porsche and a Toyota Camry, both are cars that can transport people but they were designed for different goals. You are asking how to get Toyota Camry get the acceleration, braking and comfort of Porsche.