090-252 Rev A
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pressed repeated, eventually back to the Continuous Display Mode. The user must
return to the root level before being able to switch to a different menu.
2.2.1 Main Menu
Pressing "MAIN" on the HHPC keypad brings up the Main Menu. The Main
Menu provides access to various system displays and maintenance functions.
2.2.1.1 Option 1, Regular Display
This option gives the regular display for the 6290 and is the default display on
power-up. This display shows the measure of temperature and density, along
with probe position and other important system quantities.
2.2.1.2 Option 2, Basic Units
This option displays the basic units of the system and is used in
troubleshooting or diagnostic activities. Instead of displaying temperature (a
calculated value), the resistance of the probe is displayed as received from
the Signal Conditioning Card. In addition, the actual counts are shown from
the A/D converter. Instead of displaying density, the period and frequency of
the density signal are shown. (Period is used in calculating density.) The
status of the level sensors and bottom reference is shown as a one or a zero.
For the level sensors, a one indicates that the sensors are in liquid, and a
zero indicates that they are in vapor. For bottom reference, a one means that
the bottom reference switch is activated; a zero means that it is not.
Other quantities displayed include the level sensor voltages, the temperature
of the circuit boards, and a backup reading of the voltage of the temperature
sensor in the probe.
2.2.1.3 Option 3, Motor Diagnostics
This option is another continuous display option that is used when evaluating
the performance of the motor drive mechanism. As in the regular continuous
display, the current mode of operation is displayed here, along with the
current direction and speed (if the probe is not stopped). In addition, several
pertinent quantities are displayed. The number of motor pulses from the
bottom of the tank is displayed. This is the quantity that is used to calculate
the current probe position. The reel feedback count (RFB count) is the
number of pulses the motor traveled before the reel feedback switch changed
states (either entering or leaving the magnetic field of one of the magnets).
Each time a magnet on the take up reel passes under the reel feedback
switch, a switch closure is generated. If this state change is not detected
within a certain number of motor pulses, a reel feedback alarm is generated.
The states of the level sensors and the state of the bottom reference switch
are shown as well here for convenience.
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