Campbell Scientific 253-L and 257-L (Watermark 200) Soil Matric Potential Sensors - Manual (Page 25)

253-L and 257-L Soil Matric Potential Sensors
7.2.3.3 Soil Water Matric Potential in Other Units
To report measurement results in other units, multiply the result from the linear
or non-linear equation by the appropriate conversion constant from TABLE
7-4.
TABLE 7-4. Conversion of
Matric Potential to Other Units
Desired Unit Multiply Result By
kPa 1.0
MPa 0.001
Bar 0.01
7.3 Example Programs
These examples show programs written for the CR1000 and the CR10X
dataloggers. With minor changes to excitation and voltage ranges, the code in
the CR1000 examples will work with all compatible CRBasic dataloggers (see
TABLE 7-1). The code in the CR10X examples will work with all Edlog
dataloggers as long as the correct excitation and voltage range is chosen for the
P5 instruction (see TABLE 7-2).
7.3.1 257 Program Examples
7.3.1.1 Program Example #1 — CR1000 with One 107 and One 257
The following example demonstrates the programming used to measure the
resistance (k
Ω) of one 257 sensor with the CR1000 datalogger. A 107
temperature probe is measured first for temperature correction of the 257
reading. The linear equation is used and the non-linear equation is included in
the program notes. To use the non-linear equation, remove the linear equation
from the program and uncomment the non-linear equation. Voltage range
codes for other CRBasic dataloggers are shown in TABLE 7-1. Sensor wiring
for this example is shown in TABLE 7-5.
TABLE 7-5. Wiring for Programming Example #1
Sensor Wire Function Channel
107 Black Excitation EX1
Red Positive Signal SE1 (1H)
Purple Negative Signal Ground
Clear Shield Ground
257 Black Excitation EX2
Red Positive Signal SE2 (1L)
White Negative Signal Ground
Clear Shield Ground
19