can not read some kinds of voltage signal by Scxi 1300

[hanwei]

Hi all:
 
I am just a beginner for NI DAQ, now i am using PCI-6040E, and Scxi 1001 chasis and Scxi 1102 analog input module.
 
I am wondering why sometimes I can't read some kinds of data from NI by NI Measurement & automation explore software.
 
for example:
 
I want collect voltage signals from the pressure transducer, which is just a 2v voltage signal. But I can't get it from NI, (the value is almost 0)
when I try to test other voltage signal from signal generator or battery by same channel, it is fine!
 
what ' problem about it?   Why Ni can not read some kinds of voltage signal ? anybody konw it?
 
 
thanks a lot

[hanwei]

Hi all:
 
Here I have a question about wiring. In the Pic I attached, must I connect one bias Resistor to the ground? if I want to test a floating signal (like voltage signals (across a resistor) from pressure transducer (4..20mA))


floating_connection.JPG:
Loading Image...

[RT4CY]

Hello hanwei,I understand you are having trouble reading a voltage from your pressure transducer?&nbsp; Many pressure transducers are full-bridge sensors, meaning they use internal strain gages.&nbsp; If this is the case, please check your manual for the required excitation voltage.&nbsp; You can use our <a href="http://sine.ni.com/nips/cds/view/p/lang/en/nid/4489" target="_blank">SCXI 1520 </a>module which has an independent 0 to 10 V programmable excitation source for each channel.&nbsp; Otherwise, you will have to provide your own excitation externally, then scale down to remove the excitation voltage from your signal.&nbsp; In Measurement &amp; Automation Explorer (MAX), you will create a Custom Voltage with Excitation task to read the voltage from&nbsp;the pressure transducer.&nbsp; See the following KnowledgeBase article on how to create this. <a href="http://digital.ni.com/public.nsf/allkb/FD9F22608FDC939A86256B5A0075705D" target="_blank">KnowledgeBase 2I7EBBJ3: Measuring a Full-Bridge Absolute Transducer with the SCXI-1520 or PXI-4220</a>&nbsp; If you are measuring a floating signal, it is important to provide two bias resistors to provide a path to ground from each lead.&nbsp; Please see the following Developer Zone article for more information.<a href="http://zone.ni.com/devzone/cda/tut/p/id/3344" target="_blank">Developer Zone Tutorial: Field Wiring and Noise Considerations for Analog Signals</a>