Campbell Scientific 253-L and 257-L (Watermark 200) Soil Matric Potential Sensors - Manual (Page 30)

253-L and 257-L Soil Matric Potential Sensors
'Convert resistance ratios to kOhms
kOhms(i) = kOhms(i)/(1-kOhms(i))
i = i+1
NextSubScan
PortSet(1,0) 'Turn AM16/32 Multiplexer Off
'Convert kOhms to water potential
For i = 1 To 5
'For linear equation (0 - 200 kPa) use this equation:
WP_kPa(i)=7.407*kOhms(i)/(1-0.018*(T107_C-21))-3.704
'For non-linear equation (10 - 100 kPa) uncomment and use this equation:
'WP_kPa(i) = kOhms(i)/(0.01306*(1.062*(34.21-T107_C(i)+0.0106*T107_C(i)^2))-kOhms(i))
Next i
CallTable Hourly 'Call Data Table and Store Data
NextScan
EndProg
7.3.2.2 Program Example #4 — Five 107 Temperature Probes and Five 253’s on AM16/32
and CR10X Using Non-Linear Equation
The following example demonstrates the programming used to measure five
107 temperature probes and five 253 sensors on a AM16/32 multiplexer (4x16
mode) with the CR10X datalogger. In this example, a 107 temperature probe
is buried at the same depth as a corresponding 253 sensor. The non-linear
relationship between sensor resistance and water potential in the 10 to 100 kPa
range is used. For Edlog programming of the linear relationship, see program
example #2. Voltage range codes for other Edlog dataloggers are shown in
TABLE 7-2. Sensor wiring is shown in TABLE 7-8.
TABLE 7-8. Wiring for Programming Example #4
CR10X AM16/32 Sensor Wire Function
12V 12V
G GND
C1 RES
C2 CLK
E1 COM ODD H
SE1 (1H) COM ODD L
AG COM GROUND
SE2 (1L) COM EVEN H
AG COM EVEN L
1000 ohm
resistor from
SE2 to E2
1H 107 Black Excitation
1L Red Positive Signal
GROUND Purple Negative Signal
GROUND Clear Shield
2H 253 White Positive Signal
2L Black Negative Signal
GROUND Clear Shield
Continue wiring sensors to multiplexer with 107 probes
attaching to odd numbered channels and 253 sensors to even
numbered channels.
AM16/32 in 4x16 mode.
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