(V+ + V–)/2 or the voltage remaining on the inputs when V
dm
= 0. The total
voltage on the V+ and V– inputs is given as V+ = V
cm
+ V
dm
/2, and V
L
= V
cm
–
V
dm
/2, respectively.
Measurement Accuracy
Read More For an in-depth treatment of accuracy estimates, see the technical
paper Measurement Error Analysis available at www.campbellsci.com/app-notes
(
http://www.campbellsci.com/app-notes).
Accuracy describes the difference between a measurement and the true value.
Many factors affect accuracy. This section discusses the affect percent-or-
reading, offset, and resolution have on the accuracy of the measurement of an
analog-voltage sensor signal. Accuracy is defined as follows:
accuracy = percent-of-reading + offset
where percents-of-reading are tabulated in the table Analog-Voltage Measurement
Accuracy
(p. 313), and offsets are tabulated in the table Analog-Voltage
Measurement Offsets
(p. 313).
Note Error discussed in this section and error-related specifications of the
CR1000 do not include error introduced by the sensor or by the transmission of
the sensor signal to the CR1000.
Table 56. Analog-Voltage Measurement Accuracy
1
0 to 40 °C –25 to 50 °C
–55 to 85 °C
2
±(0.06% of reading + offset) ±(0.12% of reading + offset) ±(0.18% of reading + offset)
1
Assumes the CR1000 is within factory specifications
2
Available only with purchased extended temperature option (-XT)
Table 57. Analog-Voltage Measurement Offsets
Differential Measurement
With Input Reversal
Differential Measurement
Without Input Reversal
Single-Ended
1.5 • Basic Resolution + 1.0
µV
3 • Basic Resolution + 2.0 µV 3 • Basic Resolution + 3.0 µV
Note — the value for Basic Resolution is found in the table Analog-Voltage Measurement
Resolution
(p. 313).
Table 58. Analog-Voltage Measurement Resolution
Input
Voltage Range
(mV)
Differential
Measurement
With Input Reversal
(
V)
Basic Resolution
(
V)
±5000
667 1333
±2500
333 667
±250
33.3 66.7
25 3.33 6.7
313
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