SCXI Calibration - what should be acceptance criteria for SCXI 1125

[Data Acquisition]

An interesting thing i am finding with calibration procudure of SCXI 1125.
In the table of acceptance criteria page 13 table 1. I take specific example of 1st row. Gain1, Range 5, test point 4.95, Upper limit 4.9623181 and lower limit 4.9376819. The procedure says that if I am applying test point and reads that a value between upper and lower limits, IT PASSES THE TEST !!!  Then it indicates that accuracy of instrument for present measurement is 0.25% if value.
Which is totally un-acceptable for an instrument. Now a days even sensors are available with accuracy of 0.04% accuracy. Then why should I accept your criteria of 0.25% as acceptance for PASS.

Combinely it gives me in-accuracy of 0.29%. Then how can I beleive on this measurement.

Please clarify...

[Raajit_Lall]

Hi,

You are right about the calibration ranges on that device.  It looks like you are seeing the Calibration Manual for the 1125.  The 1125 is used to measure all the way upto 300 Vrms which is a high voltage and it also has low pass filtering on each channel.  The module would typically be used for high voltage ranges and attenuating them down to a voltage that can be read by the DAQ card.  National Instruments has wide range of devices with different capabilities.  There are some high resolution DMMs and Dynamic Signal Analyser boards that provide upto 7.5 digits of resolution and better accuracy as well.  Could you please tell me what you are using the 1125 for, and what kind of accuracy are you looking for in an instrument and I might be able to provide some kind of alternative.  Also, what gain are you planning to use on the 1125.

Thank you for the information.  Looking forward to hearing from you.

Regards,

Message Edited by Raajit L on 02-05-2008 06:19 PM