QTech Data Systems SMS Controller (SMSC) - Manual (Page 6)

QTech SMS Controller - Quick Start Guide – v1.4 – February 2014 6
www.qtech.co.nz Tel: 03 3663713
Digital Outputs
The digital outputs are solid state devices designed to interface to a low power
relays. When an output is on, it will be connected to the power supply negative,
allowing current to flow into the output terminal to ground.
When in the OFF state, they have a high impedance to
ground and will float up to the power supply positive. The
digital output LED will light up when the output is ON.
To use a digital output with a relay, wire as shown in the
diagram opposite.
The maximum current available to drive all eight interface
relays is 1.5A. We suggest relays with a current of ~50mA.
Analogue Inputs
There are two analogue inputs configured for 4-20mA operation. (0-10V inputs are
available to order).
The Analogue Input LEDs show the status of the signal the RTU is receiving. If the
LED is off, it means the input signal is zero, or under-range. When the LED is on the
signal is within the measuring range that the input has been configured for. If the LED
is flashing, it shows the signal is over range.
4-20mA Devices
Any 4-20mA transducers must be powered using a separate
power supply from the analogue signal loop. If suitable, these
devices can be powered from the RTU power supply. If this is not
suitable, the analogue transducer can be powered from a
separate power supply as long as the grounds of both the RTU
and the other power supply are connected together.
Wiring of a 4-20mA device is as shown on the right.
0-10V Devices (Optional)
If your RTU is configured to use 0-10V transducers, these are
simply connected between the input and the Ground pin, as shown
on the right.
Analogue Outputs
There are two analogue outputs configured for 4-20mA operation. (0-10V outputs are
available to order).
The Analogue Output LEDs show the status of the outputs. If the LED is off the
output signal is zero. When the LED is on, it indicates the signal is greater than zero.
+ Supply
Dig Out 1
Tx
Anl In 1
G
Tx
Anl In 1
G