Analog input calibration – Measurement Computing USB-1608HS User Manual
Page 24
USB-1608HS User's Guide
Specifications
24
Note 1:
The maximum differential non-linearity specification applies to the entire 0-55 °C temperature
range of the USB-1608HS. This specification also accounts for the maximum errors due to the
software calibration (in Calibrated mode only) and the AD7685 analog to digital converter non-
linearities.
Table 2. Calibrated absolute accuracy
Range
Accuracy (mV)
±10 V
± 7.019
±5 V
± 3.509
±2 V
± 1.403
±1 V
± 0.702
Table 3. Accuracy components - All values are (±)
Range
Integral Non Linearity
(% FSR)
Gain error at FS
(mV)
Offset (mV)
Gain tempco
(ppm/°C)
Offset tempco
(µV/°C)
±10 V
0.00915
4.578
1.526
3.8
19.5
±5 V
0.00915
2.289
0.763
7.0
19.5
±2 V
0.00915
0.916
0.305
16.5
24.3
±1 V
0.00915
0.458
0.153
40.1
29.2
Note 2:
When connecting differential inputs to floating input sources, the user must provide a DC return
path from each differential input to ground. This can be accomplished by simply connecting a
resistor from each of the differential inputs to AGND. A value of approximately 100 kΩ can be
used for most applications.
Table 4. Noise performance
– all values are (±)
Range
Peak to Peak Noise
(counts)
RMS noise
LSBrms
±10 V
8
1.21
±5 V
8
1.21
±2 V
8
1.21
±1 V
8
1.21
Table 4 summarizes the noise performance for the USB-1608HS. Noise distribution is determined by gathering
50 kS with inputs tied to ground at the user connector. Samples are gathered at the maximum specified
sampling rate of 250 kS/s.
Analog input calibration
Table 5. Analog input calibration specifications
Parameter
Specifications
Recommended warm-up time
15 minutes minimum
Calibration method
Software calibration
Calibration interval
1 year
Calibration reference
+10.000 V, ±5 mV maximum. Actual measured values stored in EEPROM
Tempco: 5 ppm/°C maximum
Long term stability: 30 ppm/1000 h