User Manual

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 (kΩ) 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