We encountered a trouble during our DAQ
physical connection:
A photodiode (worked as a photocell) was shielded in a copper sheath, then connected to AI0 channel of BNC-2120(Q9 coxial jack) through a 75-3 coxial cable( RG-59/U ), we use simplest way to realise an light intensity measurement using our PXI-6221 card.
When isolated Photodiode from light, which only dark-current of photodiode accounted for, we got waveform like follows:
setting "Terminal Configuration" as "differential", we got:
http://forums.ni.com/attachments/ni/250/19905/1/NRSE.PNGas we can see, we could found an power-line frequency components (50Hz ,China) in our readings, I think our photodiode is just a floating source, so either of three measurement systems is ok, Why there is an power-line noise in our test? how to avoid it? and why "NRSE" is so different from the other two? I mean it did existed an obvious time-dependent voltage drift in the reading(higher reading-out as time passed), which measurement system shall we take in our coming measurement?
I got awfully puzzled , and need your help as soon. Our DAQ Assistant configuration is listed as following picture
chassis: PXI-1042Q
Controller: PXI-8186 @ slot0
Card: PXI-5124 at slot1
PXi-4461 @ slot2
PXI-6221 @slot3( we use this card as our A/D in this case)
BNC-2120 (as BNC Connector block of 6221)
LV PDS 7.1
NIDAQ7.4.0
帖子被wonwe在03-04-2006 02:06 AM时编辑过了
帖子被wonwe在03-04-2006 02:07 AM时编辑过了