Vertu Series VPM3000 Process Meters & Temperature Transmitters
Instruction Manual
14
Relays and 24 V Output
Connections
Relay connections are made to a six-terminal
connector labeled RELAY1, RELAY2. See Figures
. The COM
(common) terminals of the relays should not be
confused with the COM (common) terminal of the
SIGNAL connector. The 24 VDC output is available at
the connector labeled 24V OUT, next to the relays
connector.
Figure 22. Relay & 24 V Output Connections
Switching Inductive Loads
The use of snubbers to suppress electrical noise is
strongly recommended when switching inductive loads
to prevent disrupting the microprocessor’s operation.
The snubbers 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 23. 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. Inductive relay rating is 1/14 HP (50 W) at
115/230 VAC
2. Use capacitors rated for 250 VAC.
3. RC networks may affect load release time of
solenoid loads. Check to confirm proper
operation.
4. 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.
Figure 24. Low Voltage DC Loads Protection
Note:
Relays are de-rated to 1/14th HP (50 watts)
with an inductive load.
24V OUT
P+
P-
COM NO
NO
NC
NC COM
RELAY2
RELAY1
4
3
6
5
2
1
2
1
C
R
C
R
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.
