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PD9000
Multivariable Controller
20
Relay Connections
Relay connections are made to three-terminal connectors
labeled individually. There are five relays per card.
Switching Inductive Loads
The Conso has internal circuitry to protect the relays
from inductive loads, however, 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.
C
NC
NO
L
O
A
D
-
+
Internal Protection
MOV
MOV
15kΩ
4.7nF
15kΩ
4.7nF
Figure 11 AC and DC Internal Inductive Load Protection
Figure 10 Relay Connections
For additional external 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 instrument's relay screw
terminals. An RC network may also be installed
across the load. Experiment for best results.
C
NC NO
+
-
L
O
A
D
Use diode with a reverse
breakdown voltage two to
three times the circuit voltage
and forward current at least
as large as the load current.
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: PDX6901.
Serial Communication Connections
The RS-485 port for serial communication (using Modbus
protocol) has three terminals labeled D+, D-, and G. It is
strongly recommended to use three-wire shielded cable
and to always connect the ground terminal to the other
equipment’s ground to avoid differential voltage between
the systems. Distances up to 4000 feet can be reached with
RS-485. Up to 32 Modbus devices may be connected to a
single RS-485 bus.
Conso
RS-485 Port
D+
D-
G
120 ohm
B+
A-
G
120 ohm
Last Modbus
Device
Terminating Resistor
Terminating Resistor
Ethernet Option
The Ethernet port is available on the RJ45 connector. This
allows the Conso to connect to a local area network.
The Ethernet port option is configured using the System menu.
See the
for ethernet port setup
details.
External Keypad Connections
Normally open pushbuttons may be wired to the digital inputs
connector for use when the front panel of the controller is not
accessible. The external keys may be assigned to replicate
the Menu and F1-F4 function keys.
Figure 14 External Keypad Connections
G
Digital Inputs
+5V
1
2
3
4
5
External Keypad
Figure 13 Serial Connections
Figure 12 Low Voltage DC Loads Protection
C
NC NO