22
Input
Relay Energise
Relay De-energise
Trip point
Hysterisis point
Time
50%
25%
2s
2s
1) Hi alarm & Energised relay
Input
Relay De-energise
Relay Energise
Trip point
Hysterisis point
Time
50%
25%
2s
2s
2) Hi alarm & De-energise relay
Input
Relay De-energise
Relay Energise
Hysterisis point
Trip point
Time
75%
50%
2s
2s
3) Lo alarm & Energised relay
Input
Relay Energise
Relay De-energise
Hysterisis point
Trip point
Time
75%
50%
2s
2s
4) Lo alarm & De-energise relay
9. RS 485 ( ModBus ) Output (Optional)
The multifunction meter supports MODBUS (RS485) RTU protocol (2-wire) .
Connection should be made using twisted pair shielded cable. All "A" and "B" connections are daisy chained
together. The screens should also be connected to the “Gnd” terminal. To avoid the possibility of loop currents,
an Earth connection should be made at one point on the network. Loop (ring) topology does not require any
termination load. Line topology may or may not require terminating loads depending on the type and length of
cable used. The impedance of the termination load should match the impedance of the cable and be at both
ends of the line. The cable should be terminated at each end with a 120 ohm (1/4 Watt min.) resistor.
RS 485 network supports maximum length of 1.2km. Including the Master, a maximum of 32 instruments can
be connected in RS485 network. The permissible address range for the multifunction meter is between 1 and
247 for 32 instruments. Broadcast Mode (address 0) is not allowed.
The maximum latency time of an multifunction meter is 200ms i.e. this is the amount of time that can pass
before the first response character is output.
After sending any query through software (Master), it must allow 200ms of time to elapse before assuming that
the multifunction meter is not going to respond. If slave does not respond within 200 ms, master can ignore the
previous query and can issue fresh query to the slave.
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