EV/DV300 Series Power Meter
V:2.0 Revised October 2018
The setting of alarm is as following:
1. Set the relay output mode as alarm. RO=2
2. The serial number of I1 is 7 from Table 2.2.
3. CT1=200, the equation converting between real value and register value is:
Real value = (value in register×CT1÷5 )÷1000
4. Time limit is 15s. The register value is 15.
5. The value is high limit, so the sign of in equation is 1 (great than). The alarm happens
when register value > 4500.
6. The alarm relating relay is RO1, so the RO select 0. After finish above setting, the
alarm will trigger RO1 and back-light flashing when value of I1 is over 180A and last
over 15 seconds.
Communication
The communication port and protocol of EV/DV300 are RS485 and Modbus-RTU. The
terminals of communication are A, B, and S (11, 12, 13). A is differential signal +, B is
differential signal -, and S is connected to shield of twisted pair cable. Up to 32 devices can
be connected on a RS485 bus. Use good quality shielded twisted pair cable, AWG22 (0.5mm2)
or larger. The overall length of the RS485 cable connecting all devices cannot exceed 1200m
(4000ft). EV/ DV300 is used as a slave device of master like PC, PLC, data collector or RTU.
If the master does not have RS485 communication port, a converter has to be used. Normally
a RS232/RS485 or USB/RS485 is adopted. The topology of RS485 net can be line, circle and
star
The recommendations for the high-quality communication:
• Good quality shielded twisted pair of cable AWG22 (0.6mm2) or larger is very
important.
• The shield of each segment of the RS485 cable must be connected to the ground at
one end only.
• Keep cables away as much as possible from sources of electrical noise.
• Use RS232/RS485 or USB/RS485 converter with optical isolated output and surge
protection.
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