Hardware conflict?

[silver_eagle]

Hi

I am using DAQ(PCI 6220) to get two channel input( both voltage from an amplifier. the amplifier is used to amplfy the signal from conductivity and flow rate sensor. The amplifier have it built in display which  show the value of the flow rate .

The problem, very time i connect the amplifier with the data acquistion card the amplifier display straight away give me reading of 0.06( this is not the maximum value, as it been known to give reading up to 4.99), regardless any flow rate it should show. This similar reading is also shown in the test panel; using MAX. The reading using MAX show a bit noise, but the value is always constant regardless any change of the flow rate. Everytime I disconnect the DAQ from the amplifier, the display in amplifier straight away give a normal reading.

I already trying the standard trouble shooting:

1. checking all the cable connection

2. checking the DAQ card is working( by replace with a known working similar DAQ)

3. checking the amplifier, by running it independently

All seems to be working fine.Also, what I been curious that from the data sheet that I have, the DAQ should only take input and not give any output, so how it can possibly affected the amplifier built-in display?

Could anybody point me of what I need to do to fix this problem?

Thanks for the help

[Jarrod_B.]

Hello silver_eagle,

The first thing I would double-check is that you are connecting you signal to the DAQ board using the proper terminal configuration.  For this purpose, please refer to Table I in the tutorial Field Wiring and Noise Considerations for Analog Signals.  As you will see from this table, you first need to determine whether your signal source is floating or grounded.  For a floating signal source, Referenced Single Ended (RSE) is the easiest terminal configuration to use (no bias resistors required).  For a grounded signal source, use Differential mode.

If you already have the proper terminal configuration, try connecting a simple DC source to the same analog input channel and see if you are getting a good reading. 

Let us know how it goes.

Best regards,