I need to answer the following two requirements;
Gain Accuracy: The gain accuracy shall be at least ±1% of the selected dynamic range.Gain Stability: Thirty minutes after applying power to the system, the gain stability shall be better than 0.33% per minute. The total change in 1 hour shall not exceed ±3%.
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Heres the link for the technical specification sheet for the NI 6225:
The gain accuracy depends on your selected range and using the formula from the table below you can calculate the Absolute Accuracy and Gain and Offset Error.
AI Absolute Accuracy Table
AbsoluteAccuracy = Reading · (GainError) + Range · (OffsetError) + NoiseUncertainty
GainError = ResidualAIGainError + GainTempco · (TempChangeFromLastInternalCal) + ReferenceTempco · (TempChangeFromLastExternalCal)
OffsetError = ResidualAIOffsetError + OffsetTempco · (TempChangeFromLastInternalCal) + INL_Error
1 Absolute accuracy at full scale on the analog input channels is determined using the following assumptions:
TempChangeFromLastExternalCal = 10 °C
TempChangeFromLastInternalCal = 1 °C
number_of_readings = 100
CoverageFactor = 3 σ
For example, on the 10 V range, the absolute accuracy at full scale is as follows:
GainError = 75 ppm + 25 ppm · 1 + 5 ppm · 10 GainError = 150 ppm
OffsetError = 20 ppm + 57 ppm · 1 + 76 ppm OffsetError = 153 ppm
AbsoluteAccuracy = 10 V · (GainError) + 10 V · (OffsetError) + NoiseUncertainty AbsoluteAccuracy = 3,100 μV
2 Sensitivity is the smallest voltage change that can be detected. It is a function of noise.
Accuracies listed are valid for up to one year from the device external calibration.
If you have any furthur questions please do not hesitate to contact me.
National Instruments UK