35
Controller Operation
Temperature Display Hold
Temperature Display Hold
9.4
The 7102 has a display hold function which allows action of an external switch to
freeze the displayed temperature and stop the set-point from scanning. This is useful
for testing thermal switches and cut-outs.
The instrument must be powered off before
attaching thermal switches or cut-outs.
This section ex plains the functions available
for operating the temperature hold feature. An ex ample follows showing how to set up
and use the hold feature to test a switch.
Hold Temperature Display
9.4.1
The hold feature is enabled by simply pressing the “UP” button when the tem perature
is displayed. The hold temperature display shows the hold temperature on the right
and the switch status on the left. For the status “c” means the switch is closed and “o”
means the switch is open. The status flashes when the switch is in its active position
(opposite the normal position). The hold temper ature shows what the temperature of
the well was when the switch changed from its normal position to its active position.
While the switch is in the normal position the hold temperature will follow the well
temperature.
If the Scan Control is “OFF” and the Hold Temperature Display is being used, the
temperature at which the switch is activated
does not
affect the set-point temperature.
However, if the Scan Control is “ON” and the Hold Temperature Display is being
used, the temperature at which the switch is activated
is stored
as the new set-point
temperature.
Operation of the hold temperature display is outlined below.
143.50C
Well temperature display
U
Access hold display
c 144.8
Switch status and hold temperature
To return to the normal well temperature display press “DOWN”.
Mode Setting
9.4.2
The Hold Function is always in the automatic mode. In this mode the normal position
is set to whatever the switch position is when the set-point is changed. For example,
if the switch is currently open when the set-point is changed, the closed position
then becomes the new active position. The normal position will be set automatically
under any of the following conditions, (1) a new set-point number is selected, (2)
the set-point value is changed, (3) a new set-point is set through the communications
channels.
