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Beside the measuring connectors, the analog inputs have the 3.3 VDC supply voltage
connector for powering the sensor, marked as Vcc. The supply voltage is switched on
temporarily during the measurement only. This visibly decreases the energy
consumption, but requires sensors with 3.3 VDC powering. If rated supply voltage of
the sensor differs from this value, it is possible to use an external voltage source.
In case of an external powering, the common ground of an external battery should be
connected to the common wire of analog input, and output signal from the sensor
cannot exceed 3.3 VDC (i.e., the maximum value of the analog input voltage for the
MT-703
module).
4.3. Connecting supply voltage
The
MT-703
module is powered by the internal 4.5 VDC battery, consisting of 3 pieces
of 1.5 V R20 alkaline cells (6 pieces in
HC
version). The total capacity of a new battery
set is estimated as 16 Ah (32 Ah for HC). Depending on the data or SMS transmission
events rate, it allows for an autonomous operation of the module without replacing the
battery even up to 5 years.
The supply voltage is delivered by the cable with an asymmetrical plug, which fits the
socket placed on the module board in one position only.
ATTENTION!!!
Due to use of high capacity capacitor in the supply circuit, the
disconnection of supply voltage does not result in immediate switching
off the module. The activity of the module, depending on its current
state, may still extend from several seconds up to half an hour after
disconnecting the battery. Shorter discharging of the capacitor may be
achieved by pushing the ACTIVATE button.
Due to the specific, energy-saving construction of the module, it is not possible to use
other energy sources than internally mounted alkaline batteries. Especially it is
important not to use the external voltage sources connected via long cables to the
module board. Powering the module from the improper power supplies may cause the
damage of the module.
