Precision Digital PD570 - Manual (Page 21)

The condition of the output can be seen by pressing the SET/ENT as shown in the Operation Flow Chart in section 4.
The output status display refers to the condition of the limit control relay output.
The output display has two conditions, OFF and ON.
In the OFF condition:
Normally Closed (NC) Terminal: Closed
Normally Open (NO) Terminal:
Open
In the ON condition:
Normally Closed (NC) Terminal: OPEN
Normally Open (NO) Terminal:
CLOSED
To reset the limit contr ol relay after the PV has gone over limit, it must be within the set point limit. Pressing the reset
button for 3 seconds will return the limit control relay to OFF.
In the following illustration of outpu t operation, HI.LO is set to HIGH, O.ACT set to REV, and R.MD set to OFF.
The time the PV has been over the SP limit is displayed in the operation display as shown in the Operation Flow Chart
in section 4.
When the PV exceeds the SP value, the over limit timer begins operation. This will record the time that the PV is over
the SP. If the PV returns to within the SP limit, the timer will stop. If following this the PV once again exceeds the SP,
the timer w ill reset, and begin timing again.
The time passed cannot be reset while the PV is over the SP limit. If the PV is under the SP limit, the time count can
be reset with the reset key.
The timer display range is:
0.0 - 999.9 min (HH.MM)
0.0 - 999.9 sec (MM.SS)
5-2-3 Over Limit Timer
The maximum or minimum PV values are displayed in the operation display. Refer to the Operation Flow Chart in
section 4.
If set for a high limit with HI.LO set to HIGH, the maximum PV value will be displayed. If set for a low limit with HI.LO
set to LOW, the minimum PV value will be displayed. This value can be reset with the reset key while in the display
screen.
5-2-4 Maximum or Minimum PV Value Display
SP
PV
Power On
(R.MD set to OFF)
Reset
Pressed for
3 seconds
Reset Pressed
for 3 seconds
(not accepted,
PV > SP)
Fig 5: Example of Limit Control Relay Operation and Reset Function
Reset
Pressed for
3 seconds
5-2-2 Limit Status Display and Reset Functions
OUT
LED
Limit
Control
Relay
OVER
LED
ON
OFF
ON
OFF
ON
OFF
PD570 Series Nova Process and Temperature Limit Controller Instruction Manual
21