Campbell Scientific CS451/CS456 Pressure Transducer - Manual (Page 27)

CS451/CS456 Submersible Pressure Transducer
TABLE 8-3. SDI-12 Commands
SDI-12 Command Command Function Values Returned
aM! Configured settings Pressure/Level,
Temperature
aM1! PSIG, °C Pressure, Temperature
aM2! PSIG, °F Pressure, Temperature
aM3! kPa, °C Pressure, Temperature
aM4! kPa, °F Pressure, Temperature
aM5! Sensor’s Serial Number Serial Number
aM6! Ohms, ohms, °C ∆ R, Rb, Temperature
aM7! Configured settings
(provides data in less than
0.8 seconds)
Pressure/Level
aM8! Configured settings
(provides average of data
based on user selected
samples)
Pressure/Level,
Temperature
As measurement data is transferred between the probe and datalogger digitally,
there are no offset errors incurred with increasing cable length as seen with
analog sensors. However, with increasing cable length, there is still a point
when digital communications break down, resulting in either no response or
excessive SDI-12 retries and incorrect data due to noise problems. (Using
SDI-12 commands like aMC!, which adds a CRC check, can significantly
improve incorrect data issues.)
8.3 Measuring Multiple SDI-12 Sensors
Up to ten CS451/CS456 sensors or other SDI-12 sensors can be connected to a
single datalogger control port. Each SDI-12 device must have a unique SDI-12
address of 0 and 9, A to Z, or a to z. See Appendix D, SDI-12 Sensor Support,
for more information.
9. Maintenance
Campbell Scientific recommends that the CS451/CS456 be factory recalibrated
and checked every 24 months. Before a CS451/CS456 sensor is sent to
Campbell Scientific, the customer must get an RMA (returned material
authorization) number, and fill out the Declaration of Hazardous Material and
Decontamination form.
The CS451/CS456 has no user-serviceable parts. Cable can be damaged by
abrasion, rodents, sharp objects, twisting, crimping or crushing, and pulling.
Take care during installation and use to avoid cable damage. If a section of
cable is damaged, it is recommended that you send your sensor back to replace
the bale harness assembly.
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