2.3 RS 485 Parity
This screen allows the user to set Parity & number of stop bits of RS 485 port.
Pressing “ ” key accepts the present value and advances to “Quit
Communication Parameters” screen (see section 2.4).
Similarly, pressing “ ” key accepts the present value and advances to
“RS 485 Baud Rate” screen (see section 2.2).
Pressing the “ ” key advances to the “Parity & Stop bit Edit” mode &
keys “ ” and “ ” scrolls the value through:
no 1 : no parity with one stop bit no 2 : no parity with two stop bit
E : even parity with one stop bit odd : odd parity with one stop bit
Pressing “ ” key sets the value and advances to “RS 485 Parity Selection” screen (see Section 2.3).
2.4 Quit Communication Parameters
This screen allows user to exit from system “Communication
Parameter Selection” setup.
Pressing the “ ” key advances to “Communication Parameter Selection”
screen (see Section 2.1).
Similarly, pressing the “ ” key advances to “RS 485 Parity” screen (see
Section 2.3).
Pressing the “ ” key advances to “Communication Parameter Selection ”
screen (see Section 2).
3. RS 485 ( ModBus ) Output :
THE MULTIFUNCTION INSTRUMENT 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 Meter is between 1 and 247
for 32 instruments. Broadcast Mode (address 0) is not allowed.
The maximum latency time of a Meter is 300 ms i.e. this is the amount of time that can pass before the first
response character is output.
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