P
RO
V
U
™ PD6402 High Voltage & mV to Current Meter
Instruction Manual
17
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.
F4 Digital Input Connections
A digital input, F4, is standard on the meter. This
digital input should be connected with a normally
open contact across F4 and COM, or with an active
low signal applied to F4. It can be used for remote
operation of front-panel buttons, to acknowledge/reset
relays, or to reset max/min values. See
& Digital I/O Available Settings
complete list of capabilities.
Figure 22. F4 Digital Input Connections
4-20 mA Output Connections
Connections for the 4-20 mA transmitter output are
made to the connector terminals labeled MA OUT.
The 4-20 mA output may be powered internally or
from an external power supply.
Figure 23. 4-20 mA Output Connections
Analog Output Transmitter Power
Supply
The internal 24 VDC power supply powering the
analog output may be used to power other devices, if
the analog output is not used. The I+ terminal is the
+24 V and the R terminal is the return.
Figure 24. Analog Output Supply Powering Other
Devices
C
R
C
R
COM
F4
1
2
4-20 mA Input
Remote Display, PLC,
Chart Recorder, Etc.
-
+
R
I-
I+
1
3
2
RELAY1
mA OUT
24 V
12-35 VDC
Power
Supply
+
4-20 mA
Input Meter
-
+
R
I-
I+
1
3
2
RELAY1
3
2
1
-
24 V
mA OUT
Internal Power Supply
and Analog Output
3
2
1
Active Output Loop
Passive Output Loop
R
I-
I+
1
3
2
24 VDC
Powered
Device
24 V
+
-
