Specifications

Section 4. Sensor Support
4-34
Noisy signals with slow transitions through the voltage
threshold have the potential for extra counts around the
comparator switch point. A voltage comparator with 20 mV
of hysteresis follows the voltage gain stages. The effective
input referred hysteresis equals 20 mV divided by the
selected voltage gain. The effective input referred
hysteresis on the ± 25 mV range is 2 mV; consequently,
2 mV of noise on the input signal could cause extraneous
counts. For best results, select the largest input range
(smallest gain) that meets the minimum input signal
requirements.
4.7 SDI-12 Measurements
Read more! Section 11.3 SDI-12 Sensor Support and Section 10.11 Serial
Input/Output.
SDI-12 is a communications protocol developed to transmit digital data from
smart sensors to data acquisition units. It is a simple protocol, requiring only a
single communication wire. Typically, the data acquisition unit also supplies
power (12V and ground) to the SDI-12 sensor. The CR1000 is equipped with
four SDI-12 input channels (C1, C3, C5, C7) and an SDI12Recorder()
CRBASIC instruction.
4.8 RS-232 Measurements
Read more! See Section 11.8 Serial Input.
Many smart sensors output digital data through an RS-232 protocol. The
CR1000 is equipped to read the output of most RS-232 sensors on the 9-pin
RS-232 port or on four communications ports configured from digital I/O
ports, i.e., C1 & C2, C3 & C4, C5 & C6, C7 & C8. RS-232 data must usually
be read then parsed.
4.9 Field Calibration of Linear Sensor
Read more! Section 11.1 FieldCal has complete FieldCal information.
Calibration increases accuracy of a measurement device by adjusting its output,
or the measurement of its output, to match independently verified quantities.
Adjusting a sensor output directly is preferred, but not always possible or
practical. By adding FieldCal() or FieldCalStrain() instructions to the CR1000
program, a user can easily adjust the measured output of a linear sensors by
modifying multipliers and offsets.
CAUTION