2.2 External power supply, voltage/current measurement
The device can be supplied from one CR2032 battery and/or from Vbat terminal. When Vbat terminal
is connected, the batteries are only used as a backup power source in case external voltage is discon-
nected.
Vbat input (referenced to the GND terminal) is also used as an analog voltage input. The input
can measure voltages from 0 V to 60 V.
Current measurement can be achieved by measuring the dropout voltage on an external
shunt resistor. The shunt resistor can be placed either in positive (high-side) or negative (low-side)
terminal of the measured circuit. Select a shunt resistor which at maximum current does not exceed
the shunt input differential voltage range of ±80 mV. The current measurement is bi-directional, show-
ing current flow in both directions. Figures 2.2A and 2.2B show high-side and low-side current meas-
urement.
The system is pre-configured for 500A/50mV shunts. If you install a different value, please report your
shunt value to support@sentinelmarine.net.
2.3 Engine RPM input
RPM input is designed to work with an alternator's RPM pulse ouptut, most commonly marked "W".
Alternator's pulse ouptut is a scaled representation of actual RPM, which is often called a "pulse code".
Default engine pulse code is set to 10.7. In case your alternator has a different pulse ratio, please con-
tact support.
High side current measurement2.2A Low side current measurement2.2B
Rsh hi
Rsh lo
RPM in
+Vbat
GND
SW1
SW2
IN 1
IN 2
Rsh hi
Rsh lo
RPM in
+Vbat
GND
HUB
Shunt resistor
Load
Rsh hi
Rsh lo
RPM in
+Vbat
GND
SW1
SW2
IN 1
IN 2
Rsh hi
Rsh lo
RPM in
+Vbat
GND
HUB
Shunt resistor
Load
RPM input is also used as an engine hours counter, counting the cumulative time the engine was oper-
ating.
When using the Hub to measure RPM, please connect the +Vbat supply line as well in order to ensure
the correct operation.
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