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connected, the type of cable used, and the environment of the application. Follow these
guidelines when using long cables:
Use low capacitance, low resistance, screened cable (as fitted by Campbell Scientific) to
l
reach distances of several hundred metres.
Ensure that the power ground cable has low resistance and is connected to the same
l
ground reference as the data logger control terminals.
Be aware that daisy-chaining sensors reduces the maximum cable length roughly in
l
proportion to the number of sensors connected in parallel.
8.3 Modbus register map
Table 8-1
(p. 18) provides the input register map (function code 4) and
the holding register map (functions 3, 6, and 16).
Table 8-1: Input register map
Input register
30001
30003
30005
30007
30009
Modbus float is a 32-bit integer.
1
CS240 and CS240DM PT-1000 Class A, Back-of-Module Temperature
Value
Serial number
Temperature
Counter
Sensor status
Temperature
range check
Modbus
data type
Specifies the sensor serial number
1
Float
assigned by the factory
1
Float
The stored value is in degrees Celsius.
The counter provides an indicator
that the sensor is actively taking
1
Float
measurements. This value will
increment once per measurement,
resetting to 0.
0 = good
1
Float
1 = open/short
0 = good/in range
1
Float
1 = out of range
Table 8-2
(p. 19) provides
Description
Sensors 18
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