Helios PD2-6400 High Voltage & High Current Meter
Instruction Manual
18
Switching Inductive Loads
The use of suppressors (snubbers) is strongly
recommended when switching inductive loads to
prevent disrupting the microprocessor’s operation.
The suppressors also prolong the life of the relay
contacts. Suppression can be obtained with resistor-
capacitor (RC) networks assembled by the user or
purchased as complete assemblies. Refer to the
following circuits for RC network assembly and
installation:
Figure 20. AC and DC Loads Protection
Choose R and C as follows:
R: 0.5 to 1
Ω for each volt across the contacts
C: 0.5 to 1 µF for each amp through closed contacts
Notes:
1. Use capacitors rated for 250 VAC.
2. RC networks may affect load release time of
solenoid loads. Check to confirm proper
operation.
3. Install the RC network at the meter's relay screw
terminals. An RC network may also be installed
across the load. Experiment for best results.
Use a diode with a reverse breakdown voltage two to three
times the circuit voltage and forward current at least as large
as the load current.
Figure 21. Low Voltage DC Loads Protection
RC Networks Available from
Precision Digital
RC networks are available from Precision Digital and
should be applied to each relay contact switching an
inductive load. Part number:
Note: Relays are de-rated to 1/14th HP (50 watts)
with an inductive load.
RS-485 Connections
The RS-485 connections are made to a five terminal
connector used for Modbus
®
RTU serial
communications. The RS-485 terminals include
Transmit Data (DO) and (/DO), Receive Data (DI) and
(/DI), and Signal Ground. See
information.
There are three diagnostic LEDs: Power (PWR)
Transmit Data (TX), and Receive Data (RX) to show
when the meter is transmitting and receiving data
from other devices.
Figure 22. RS-485 Connection
RS-485 Multi-Drop Connection
When using more than one meter in a multi-drop
mode, each meter must be provided with its own
unique address. The meter address (Slave ID) can be
programmed between 1 and 247. The transmit delay
can be set between 0 and 199 ms. The parity can be
set to even, odd, or none with 1 or 2 stop bits.
To change the meter address:
1. Press and hold the Menu button for three
seconds to access Advanced Features menu of
the meter.
2. Press Up arrow until Serial (
SEriaL
) menu is
displayed and press Enter,
Addres
is displayed.
3. Press Enter to change meter address using Right
and Up arrow buttons. Press Enter to accept.
4. Press Menu button to exit and return to Run
Mode.
RS-485 Serial Converters
To convert the RS-485 to RS-232, use the PDA7485-I
converter. To convert the RS-485 to USB, use the
PDA8485-I converter. See
C
R
C
R
RS-485
PWR
TX
RX
DI
DI DO DO
__ __
