USER MANUAL
TYPE ML-2012/13
Manufacturers of low power instruments
page 36
5.3 Pin Description
5.3.1 Analog Inputs
Analog Input 1 to 4
These are Current-inputs, with an input impedance of 15 ohms. The range is 4 .. 20 mA. The circuits are
equipped with over current-protection. To use this input connect the + of the sensor to the + of the power
switch and the – of the sensor to the analog input pin.
Analog Input 5 to 8 (ML-2013 only)
These are differential voltage-inputs, with an input impedance of 1 Mohms. The max. range is 4 ..
2000mV. To use this input connect the + of the sensor to the + input and the – of the sensor to the –
input.
There are some terminals which hold ground level, This provides both sensor-ground and battery ground.
For your convenience, these terminals are connected to multiple pads on the connector PCB, because
every single sensor will need his own ground. You can connect multiple sensors. When more connections
are needed, just connect a wire from there and put the additional connections in parallel.
5.3.2
RS 485 A & B
These are the pins for RS485 communication. Use these pins together with a ground signal. These
signals are ESD-protected by the driver-circuit. The signal levels are according to the
TIA/EIA-485
Standard.
5.3.3
Power Switch
This is an output to drive one or more sensors. It holds a level of 12 Volts and is capable of driving up to
200 mA.
5.3.4
VBAT +
This is the main power supply input for the board. The level is 3.6 Volts.
Note: This signal is NOT the same as the internal 3.6 volts level. The power-supply circuit converts this
level to the fixed, internal, 3.6 Volts level. This voltage level is allowed to be between 0.8 volts and 5
Volts. We strongly recommend using a 3.6 Volts Power source only. The actual voltage on this pin is
monitored by the firmware. It is called “Primary input Voltage”. Also the current, flowing through the 2
wires, is monitored, and is called “Primary input Current”.
5.3.5
RX & TX COM 1 & Com 3
These are the pins for RS232 communications. Use these pins together with ground. Al pins are
protected against ESD. Voltage levels are according RS232 standard.
5.3.6
SDI-12 Hi
This is the in/out terminal for SDI-12 communication. It is protected against overvoltage. Use this terminal
together with ground. See
www.sdi-12.org
for more information.
5.3.7
Digital inputs
These are interrupt-driven inputs, with an internal pull-down resistor. To use it, connect a switch between
the 3V6 and this terminal. It is suitable for energy meters, water meters and rain-gauges.
5.3.8
+3V6
This is a power output. It is used to power external sensors or a potentiometer. It has a voltage of 3.6
Volts and is capable of driving up to 100 mA.
