T-Surface Sensor
3
Wiring Examples:
Campbell Data Logger (CR1000)
This section describes how to connect the T-Surface sensor to the widely used Campbell
data logger CR1000. If you use another data logger, contact us in case you need further
assistance. The T-Surface sensor can be connected in differential voltage as well
as in single-ended voltage mode, measurement range must be set to 2500 mV. One
CR1000 can record up to eight T-Surface sensors in differential mode, or sixteen T-
Surface sensors in single-ended mode.
Differential Voltage Mode T-Surface sensor
Connection
Cable Color
Input Port
1
st
T-Surface
sensor
V
T-Surface
White
Vx1
Brown
1H
Black
1L and Signal Ground
Program Syntax (exemplifying one sensor, with conversion of raw voltage signal in °C)
VoltDiff(T_Soil,1,mV2500,2,True,0,_50Hz,1,0)
T_Soil=(2500-T_Soil)/T_Air*20000
T_Soil=1/(0,000,000233897*LN(0,000000088*LN(T_Soil)^3)-273.15
DL 18 data logger
Ordered with stereo plug connector, the T-Surface is compatible with our DL 18 data log-
ger. Each T-Surface sensor requires one of the four channels of the DL 18. For further in-
formation on DL 18 configuration for T-Surface sensors, please refer to our DL18 manual.
Configured correctly, sensor signals will be stored in V. Values in °C can be calculated
from stored measurement values as described in the following section (Excel program for
data calculation available on request).
5. Manual Data Calculation
In case that the used logger does not support complex conversion procedures of the raw
measurement values, stored values have to be converted manually after data download
from the logger (e.g. DL 18 logger).
The following function applies to convert the analog output signal of the T-Surface sensor
from
V into Ω:
R
ntc
=(V
ex
-V
out
)/V
out
*20000
where:
R
ntc
: NTC sensor resistance in
Ω corresponding to the respective mV measurement signal
V
ex
: excitation Voltage in V (e.g. for DL 18 logger V
ex
= 2.5 V)
V
out
: measured sensor output signal in V, ranging between 0 and V
ex
The following function applies to convert the analog output signal
from Ω into °C:
T (°C)= 1/(a + b(Ln R
ntc
) + c(Ln R
ntc
)^3)-273.15 (Steinhart-Hart equation)
where:
T: temperature in °C
R
ntc
: sensor resistance in
Ω at temperature T
a: coefficient = 1.13075635 E-03
b: coefficient = 2.33896902 E-04
c: coefficient = 8.82996895 E-08
