Dear all,
I faced a problem during the time of Acquisition for measuring the voltage signal (Range: 1mv to 15volts) through NI-DMM (PXI-4070).That voltage was obtained form the UUT. The complete details of that problem are as follows:
1.) I measured the voltage signal Parallel with both NI-DMM Cards and Agilent DMM (through GPIB). While Acquiring the Data sampling rate for the both NI and Agilent DMM'S are same (i.e., at 1 sample/sec).I acquired the data for 60 Sec for each rotaion.For the Calculations Averaging the middle of the 60 sec data. The results coming from the UUT are not matching with NI & Agilent .The obtained results from NI & Agilent DMM'S are shown in [DATA& Graph figure.]
2.) I calculate the slope and intercept values of Average data and the rotations for both Ni & agilent DMM'S by using the Linearity-Fit, Which was shown in the [DMM-DATA figure.].The slope values for both Ni & agilent DMM's are same but the intercept values are different. Those calculations details are shown in[ DATA& Graph.]
3.) Depending upon the intercept value and the voltage data coming from the DMM, the linearity curve will be obtained. The linearity curves for the both NI & AGILENT DMM'S are shown in [Linearity Curves figure (3)],and linearity values for different rotations are calculated by using the following formula:
Linearity(L)= [(R*S+I)-D] / S ;
Where R=Rotations ,S=slope,I= Intercept, D=DMM voltage value for that particular rotation.
The linearity values for different rotations are shown in [Linearity data figure].
4.) While Acquiring the Voltage Data the following configuration is used
DMM configuration
Voltage range: 100 V
Resolution : 6 1/2
Multi point configuration
Sample count : 0
Multi point read
Number to read : 2
Maximum Time : 1000 milli sec
