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CS451/CS456 Submersible Pressure Transducer
TABLE 7-5. 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
Δ
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.)
7.1.5.1 SDI-12 Addresses
Multiple sensors can be connected to a single digital I/O channel (control port)
on an SDI-12-compatible datalogger; each sensor must have a unique SDI-12
address. Possible addresses are 0 to 9, A to Z, and a to z.
The CS451/CS456 is shipped from the factory with the address set to 0. The
address on the CS451/CS456 can be changed by sending an SDI-12 change
address command ‘aAb!’, where a is the original address and b is the new
address. The change address command can be issued from most SDI-12
recorders.
To change the address of a sensor that has a default address of 0 to the address
of 1 the following command can be sent:
0A1!
When it is necessary to measure more than one CS451/CS456, it is easiest to
use a different control port for each CS451/CS456 instead of changing the
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Содержание CS451
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