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A combined irradiance and cell temperature sensor (Si-420TC-T) with precongured
measuring inputs is available from Sputnik Engineering. Connect the sensor to the
expansion port as follows:
Signal Wire colour Expansion port terminal
GND black GND
V+ red V+
Irradiance orange AD0
Cell temperature brown AD1
For other sensors adjust the measuring input parameters as required. To this end you
need the linear equation for sensor, which is determined as follows:
Linear equation y(x) = mx + b, with m representing the gradient and b the offset.
Equation for gradient m:
y(20 mA) − y(4 mA)
777.06667
m=
Equation for offset b:
b= y(4 mA) − m · 194.2666
Example: Temperature sensor 4…20 mA = −50 °C…+50 °C
50 − (−50)
777.0667
m= = 0.1287
b= (−50) − 0.1287 · 194.2666 = −75
For the temperature sensor you would therefore have to enter 0.1287 for the gradient and
−75 for the offset.
Once the sensors are activated they appear in the system data as “MaxMeteo EP” and are
allocated the rst free address.
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