Campbell CR800 Series, Operator'S Manual

Page: 367 / 598

Section 8. Operation
367
Analog Voltage Measurement Resolution
Input
Voltage Range
(mV)
Differential
Measurement
With Input Reversal
(
µ
V)
Basic Resolution
(
µ
V)
± 5000
667 1333
± 2500
333 667
± 250
33.3 66.7
25 3.33 6.7
7.5 1.0 2.0
2.5 0.33 0.67
Note — see Specifications
(p. 91)
for a complete tabulation of measurement
resolution
As an example, figure Voltage Measurement Accuracy Band Example
(p. 329)
shows changes in accuracy as input voltage changes on the ±2500 input range.
Percent-of-reading is the principle component, so accuracy improves as input
voltage decreases. Offset is small, but could be significant in applications
wherein the sensor-signal voltage is very small, such as is encountered with
thermocouples.
Offset depends on measurement type and voltage-input range. Offsets equations
are tabulated in table
Analog Voltage Measurement Offsets
(p. 328).
For example,
for a differential measurement with input reversal on the ±5000 mV input range,
the offset voltage is calculated as follows:
offset = 1.5 • Basic Reso 1.0 µV
= (1.5 • 667 µV ) + 1.0 µV
= 1001.5 µV
where Basic Resolution is the published resolution is taken from the table Analog
Voltage Measurement Resolution
(p. 328).