Calculate uncertainty of PCI-6034E

[ginos]

Hallo, I am trying to calculate the overall uncertainty of DAQ System, which has a PCI-6034E board and an SCXI-1102B. I know about the accuracy calculator and I am trying to check my results using this tool.

I use K thermocouples in a temperature range 30-90℃ in an ambient temperature of about 30℃, which corresponds to a input signal range 1,203mV-3,682mV.

The calculation formula is: Absolute Accuracy = +/-[(Input Voltage x % of Reading)+ Offset +System Noise +Temperature Drift]

At first I set to the accuracy calculator: DAQ device to PCI-6034E and SCXI module to none. Then I set for example 0.001203V and Average of 100 readings.The result is the following:

According to the E Series User Manual (page 38 gain+resolution PCI-6034E) Absolute Accuracy=0,001203*0,0588/100+ (28,9 +2,75)*10^-6=0,03235mV

which the same with the accuracy calculator.

I I set to the accuracy calculator: DAQ device to PCI-6034E and SCXI module SCXI-1102B, then i do not get the same results about the absolute accuracy of the DAQ device.

Accuracy Calculator:

 

Me: DAQ Absolute Accuracy=0,1203*0,0588/100+ (100 +5,04)*10^-6=0,175mV which I a very large number. I assume that the input value is 0,1203 because the gain of the scxi 1120b is 100.

What I am doing wrong?

Furthermore, I cannot find detailed specification about scxi-1102b in the user manual (Offset in Single Point and in average of 100 readings).

Thank you very much,

Giorgos P.

[Jim_S · Accepted solution]

Hello Ginos,

I went over your calculations and you have calculated the accuracy correctly. The DAQ absolute accuracy at .5 to -.5 is .175mV but they have converted this value so that it has meaning to the orginal signal. The original signal acquired by the SCXI-1102B was multiplied by a gain of 100. After this gain, the signal is sent to the DAQ card to be digitized into your computer.

In order to relate this digitized signal accuracy to the original signal, they divided it by the gain given by the SCXI-1120B module. This is why there is a factor of a 100 difference between the two.

[ginos]

Ok this make sense.

Do you know where else can I find detailed info about the SCXI-1102B such as the specs of the PCI-6034E?

Thank you very much Jim!