8.5.1 Hold TemperatureDisplay
When the hold feature isenabled you can easily switch the display between the
normal temperaturedisplay and the hold temperature display by simply press-
ing the“UP” or “DOWN”buttons. 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 activeposition (opposite the normal position).
The hold temperatureshows 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.
Operation of the hold temperature display is outlined below.
43.56 C Well temperature display
UAccess hold display
c 44.8C Switch status and hold temperature
Note that the hold function display is not accessible if the function mode is set
to “OFF”. (See Section 8.5.2)
Toreturn to the normal well temperature display press “DOWN” or “EXIT”.
8.5.2 Mode Setting
The temperaturehold feature has three modes of operation. In the nor-
mally-closed (n.c.) mode the hold temperature display freezes when the switch
opens. In thenormally-open (n.o.) mode the hold temperature display freezes
when the switch closes. Wheneverth es witch isin th en ormal position the hold
temperature follows the well temperature.
There is also an automatic mode. In this mode the normal position is set to
whateverthe switch positio n isw hen 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 activeposition. Th e normal position will be set automati-
cally under anyof the following conditions, (1) a new set-point number is se-
lected,(2) theset-point value is changed, (3) a new set-point is set through the
communicationschannels, or (4) the ramp-and-soak program is running and
automaticallysteps to the next set-point in the sequence. The automatic mode is
useful for repetitivetests of the o pening and closing temperatures of a switch.
The temperature hold feature can also be disabled by setting the mode to
“OFF”.
The operating modeof the temperaturehold is set in the primary menu after the
scan rate setting.
28 HartScientific
8Controller Operation