PRECISION DIGITAL ProVu PD7000, Instruction Manual

Page: 25 / 40

P
RO
V
U
™ PD7000 Temperature Meter
Instruction Manual
25
Time Delay Operation
The following graphs show the operation of the time
delay function.
When the signal crosses the set point, the On time
delay timer starts and the relay trips when the time
delay has elapsed. If the signal drops below the set
point (high alarm) before the time delay has elapsed,
the
On time delay timer resets and the relay does not
change state. The same principle applies to the Off
time delay.
Note: If
“
Automatic or Manual (
A-nmAn
)
”
reset mode is
selected, the LED follows the reset point and
not the relay state when the
relay is acknowledged.
Relay Operation Details
Overview
The relay capabilities of the meter expand its
usefulness beyond simple indication to provide users
with alarm and control functions. These capabilities
include front panel alarm status LEDs as well as
either 2 or 4 optional internal relays and/or 4 external
relays expansion module. Typical applications include
high or low temperature alarms, control applications
such as simple on/off temperature control. There are
four basic ways the relays can be used:
1. High or Low Alarms with Latching or Non-
Latching Relays
2. Simple On/Off Control with 100% Adjustable
Deadband
3. Sampling (Based on Time)
4. Relay Alternation Control
Relays Auto Initialization
When power is applied to the meter, the front panel
LEDs and alarm relays will reflect the state of the
input to the meter. The following table indicates how
the alarm LEDs and relays will react on power-up
based on the set and reset points:
Alarm # HI or LO
Alarm
Set
Point
Reset
Point
Power-
Up
Reading
Relay &
LED
1 HI 1000 500 499 Off
2 LO 700 900 499 On
3 LO 250 400 499 Off
4 HI 450 200 499 On
Fail-Safe Operation
The following table indicates how the relays behave
based on the fail-safe selection for each relay:
Fail-Safe
Selection
Non-Alarm State Alarm State
Power
Failure
NO NC NO NC
Off Open Closed Closed Open Relays
go to
non-
alarm
state
On Closed Open Open Closed Relays
go to
alarm
state
Note: NO = Normally Open, NC = Normally Closed.
This refers to the condition of the relay contacts
when the power to the meter is off.