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SCXI_1540 excitation voltage 1.675 Vrms instead of called for 3Vrms
CytecHDG-rwv
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05-27-2004 02:17 PM
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I am running LabVIEW 7.0 with DAQ 7.2 (just updated the DAQ).
I am running an SCXI-1000 Chassiss with the following cards:
SCXI-1112
SCXI-1520 w/ 1314 terminal block.
SCXI-1540 w/1315 terminal block.
I first noticed a problem when I tried to calibrate/verify the travel of my LVDT on the SCXI-1540 using a simple VI that allows me to set the LVDT core to null before displacing the probe using a calibrated linear micrometer.
I was/am getting readings that are incorrect.
I corresponded via email with a technical support engineer - but that is a slow medium; having to wait for my emails to be filtered through a system...
He suggested that either my LVDT specifications for sensitivity were in
correct or perhaps my hardware needed to be calibrated. I check the voltage output and frequency of the channel I am using on the 1540/1315 (which is channel 2) and the Voltage is only 1.675 Vrms, versus the called for 3.0 Vrms that the VI is asking for (the excitation is set sourced to internal) - and the Frequency I saw on the Excitation channel was 10,360 Hz.
How do I go about correcting this offset?
Ryan Vallieu
I am running an SCXI-1000 Chassiss with the following cards:
SCXI-1112
SCXI-1520 w/ 1314 terminal block.
SCXI-1540 w/1315 terminal block.
I first noticed a problem when I tried to calibrate/verify the travel of my LVDT on the SCXI-1540 using a simple VI that allows me to set the LVDT core to null before displacing the probe using a calibrated linear micrometer.
I was/am getting readings that are incorrect.
I corresponded via email with a technical support engineer - but that is a slow medium; having to wait for my emails to be filtered through a system...
He suggested that either my LVDT specifications for sensitivity were in
correct or perhaps my hardware needed to be calibrated. I check the voltage output and frequency of the channel I am using on the 1540/1315 (which is channel 2) and the Voltage is only 1.675 Vrms, versus the called for 3.0 Vrms that the VI is asking for (the excitation is set sourced to internal) - and the Frequency I saw on the Excitation channel was 10,360 Hz.
How do I go about correcting this offset?
Ryan Vallieu
05-28-2004 10:45 AM
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I ran through the "test panel" http://digital.ni.com/public.nsf/websearch/d019c2838033c57786256a150054f385
and shorted the channel and performed the tests described above and the chan-chan test performed fine, good results.
The Ex-Chan test showed that the Vrms was 2.825 more than the recommeded different in the linked instructions.
and shorted the channel and performed the tests described above and the chan-chan test performed fine, good results.
The Ex-Chan test showed that the Vrms was 2.825 more than the recommeded different in the linked instructions.
AgwaNoa3
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06-16-2004 02:26 AM
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Actually I am having the same problem that the above client has, and I tried the test that CytecHDG-rwv mentioned and got even better results than he did, but the readings are still wrong,
I sent the module to be tested by NI in the USA, they returned it (after 40 days!) saying that there is nothing wrong with it,
and I'm still getting the wrong results!
I am using two different AC-AC LVDTs and I'm not getting the right readings from both.
If any body can find a solution for this trouble I would be thankful.
I sent the module to be tested by NI in the USA, they returned it (after 40 days!) saying that there is nothing wrong with it,
and I'm still getting the wrong results!
I am using two different AC-AC LVDTs and I'm not getting the right readings from both.
If any body can find a solution for this trouble I would be thankful.
06-16-2004 08:49 AM
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I just sent my board in for calibration to NI.
I will post back when I get it back from them and get to try it again.
I will post back when I get it back from them and get to try it again.
06-16-2004 08:52 AM
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Oh and actually my readings were not that far off, it turns out that the Fluke Multimeter that my maintenance dept. lent to me was not designed to handle 10,000 Hz signals.
I then used a scopemeter (similar in function to oscilliscope) to check the Vrms, Frequency and Peak voltages, they were closer to 3 Vrms, but the page on the SCXI-1540 stated +/- .002V should be the target variation, I was getting 3.06, and my frequency was always higher no matter what frequency I selected in my channel. At 10,000 Hz selected I was typically seeing 10,360 Hz from the board. At 5,000 Hz excitation selected I was seeing 5250 Hz, etc.
I then used a scopemeter (similar in function to oscilliscope) to check the Vrms, Frequency and Peak voltages, they were closer to 3 Vrms, but the page on the SCXI-1540 stated +/- .002V should be the target variation, I was getting 3.06, and my frequency was always higher no matter what frequency I selected in my channel. At 10,000 Hz selected I was typically seeing 10,360 Hz from the board. At 5,000 Hz excitation selected I was seeing 5250 Hz, etc.
