Senquip ORB-X1-G, User Manual

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Chapter
6
External Sensors
6.1 Current Source 1 and 2
Two 12V switched current sources, which can source a maximum of 200mA each are supplied on pins 3
and 5. The 12V supply is internally generated and is battery backed and so can still be used when
running of solar or battery power. Current supplied by each of the switched current sources is measured
to a resolution of 0.1mA and so is able to be used to supply and measure the output of 4-20mA and other
current-output sensors. Internal resettable fuses protect the outputs against over-current events.
The switched current sources are expected to be used to power external sensors such as hall-effect
sensors, 4-20mA sensors and serial devices. It can be configured to turn on prior to measurement to allow
sensors time to boot or for measurements to stabilise. After measurements are complete, the output can
be switched off to preserve power; this is especially important when running off solar or batteries. The
current sources can be used to power a sensor that is measured using one of the inputs, since the inputs
are measured just before the current sources are turned off.
Note When a current source is used to power a sensor that is read by an input, the intervals specified for
the current source and input must be the same.
Many 4-20mA sensors are powered by the current flowing through the loop to which they are connected
and are called loop powered devices. Loop powered sensors can be connected using switched source 1 as
the current source (pin 3) and GND (pin 2 or 4) or alternatively using switched source 2 as the current
source (pin 5 as shown below) and GND.
Figure 6.1. Connecting a single loop powered device
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