Precision Digital Corporation PD6820, Instruction Manual

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PD6820 Explosion-Proof Loop-Powered Rate/Totalizer
Instruction Manual
9
Wiring Diagrams
Signal connections are made to a four-terminal
connector mounted in the base of the enclosure per
Figure 3. Connector Board . The enclosure also
provides one internal and one external earth
grounding screw.
For installations that don’t use the backlight, the
maximum voltage drop is 3 V and connections are
made per
Figure 4.
For installations that use the backlight powered from
the meter, the maximum voltage drop is 6 V and
connections are made per
Figure 5
.
For installations that use the backlight powered from
an external source, the maximum voltage drop is 3 V
and connections are made per
Figure 6
.
Figure 4. Connections without Backlight
Figure 5. Connections with Loop-Powered Backlight
Loop-powered backlight brightness will increase as
the input signal current increases. If constant back-
light brightness is desired, the backlight should be
powered by an external source.
Figure 6. Connections with Externally-Powered Backlight
It is possible to use the same transmitter (signal loop)
power supply for the externally powered backlight.
The backlight circuit will draw 25 mA in addition to the
loop circuit.
External Reset Connection
External reset connections are made to two terminals
labeled RESET. Connect to a contact closure source
such as a relay or a pushbutton as shown in
Figure 7
.
Figure 7. Reset Connections
Open Collector Output Connections
Output connections are made to two terminals labeled
OUTPUT. Connect to an input device such as alarm
indicator or pulse counter as shown in
Figure 8
or drive
a relay as shown in Figure 9 .
To avoid damaging the PD6820’s amplifying
components, use care not to wire incorrectly or
exceed output ratings. A diode, such as 1N4000
series, will provide protection from relay transients.
Figure 8. Connection to Device with Internal Pull-Up
Figure 9. Output Connections
4-20 mA
Transmitter
+ - + -
SIGNAL BACKLIGHT
Power
Supply
UNLOCK LOCK
SAFE-TOUCH
BUTTONS
LOOP 9-36
VDC
BACKLIGHT
POWER
+ -
+ -
OUTPUT RESET
UNLOCK LOCK
SAFE-TOUCH
BUTTONS
LOOP 9-36
VDC
BACKLIGHT
POWER
4-20 mA
Transmitter
+ - + -
SIGNA L BACKLIGHT
Slide Switch to
LOOP
Power
Supply
+ -
+ -
OUTPUT RESET
4-20 mA
Transmitter
+ - + -
SIGNA L BACKLIGHT
Slide Switch to
9-36 VDC
Power Supply
Power
Supply
+ -
+ -
OUTPUT RESET
UNLOCK LOCK
SAFE-TOUCH
BUTTONS
LOOP 9-36
VDC
BACKLIGHT
POWER
+ - + -
SIGNA L BACKLIGHT
+ - + -
OUTPUT RESET
UNLOCK LOCK
SAFE-TOUCH
BUTTONS
LOOP 9-36
VDC
BACKLIGHT
POWER
+ - + -
SIGNA L BACKLIGHT
+ - + -
OUTPUT RESET
+
Alarm Indicator/
Pulse Counter
(e.g. PD6300)
-
UNLOCK LOCK
SAFE-TOUCH
BUTTONS
LOOP 9-36
VDC
BACKLIGHT
POWER
+ - + -
SIGNA L BACKLIGHT
+ - + -
OUTPUT RESET
UNLOCK LOCK
SAFE-TOUCH
BUTTONS
LOOP 9-36
VDC
BACKLIGHT
POWER