Campbell Scientific CR3000 Micrologger - Manual (Page 284)

Section 8. Operation
284
Table 53. CRBasic Parameters Varying Measurement Sequence and
Timing
CRBasic Parameter Description
MeasOfs Correct ground offset on single-ended measurements.
RevDiff Reverse high and low differential inputs.
SettlingTime Sensor input settling time.
Integ Duration of input signal integration.
RevEx Reverse polarity of excitation voltage.
8.1.2.4 Measurement Accuracy
CR3000 analog-measurement error is calculated as
Error = Gain Error (%) + Offset Error
Gain error is expressed as ±% of reading and is a function of CR3000
temperature. Between 0°C and 40°C, gain error is ±0.04% of input voltage. This
gain error assumes factory recalibration every two years.
Offset error depends on measurement type and input range. For differential
measurements with input reversal,
Offset Error = 1.5 • Resolution + 1.0 µV
where
Basic Resolution is the published resolution of the programmed input
voltage range (see CR3000 Specifications
).
Figure CR3000 Voltage Measurement Accuracy
(p. 285)
illustrates that as magnitude
of input voltage decreases, measurement error decreases.
Note The accuracy specification includes only the CR3000 contribution to
measurement error. It does not include the error of sensors.
For example, assume the following (see CR3000 Specifications ):
• Input Voltage: 5000 mV
• Programmed Input Voltage Range: ±5000 mV (
mV5000 )
• Programmed Measurement Instruction: VoltDiff()
• Input Measurement Reversal:
True
• CR3000 Temperature: Between 0°C and 40°C
Accuracy of the measurement is calculated as follows:
Error = Gain Error + Offset Error,
where
Gain Error = ± (5000 * 0.0004)