Suggested Sun output connections
There are several possible ways of connecting up the SPN1 Sun output,
depending on the capabilities of your data logger. The Sun output is open
circuit when there is no sun, and connected to ground when there is sun.
1 Logger digital input
In general this will be the simplest connection if your logger has a
digital input. Connect as shown in the previous two diagrams. The
logger digital input is usually referenced to logger ground, so you
should take care only to connect this to SigGND if the logger is not
supplying power for the SPN1. Otherwise, power supply currents may
flow through the SigGND cable, which may cause voltage offsets on
the Total and Diffuse readings with long cable lengths.
2 Logger resistance input
If the logger has no digital inputs, but can measure resistance, then
the Sun output can be measured with a 10k resistor connected in
parallel. This will be measured as 10k with no sun, and 0k with sun
present. Disable any autoranging on the input.
Note : The following scheme is for illustration only. Refer to your own
logger user manual for the correct wiring instructions, which may be
different.
CH1+
CH1-
PWR
GND
5V
Datalogger
Analogue input
10k
(Resistance)
SigGND
Sun
SPN1 User Manual v1.0
Introduction
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