PCM-2 Manual.pdf - Voss Associates

Computer Interface
The user is instructed to enter the first counting position as depicted on position
display number one. This requires the user to face into the detectors and look to
the right, toward the active position display. If feet, hands or body are not in
close contact with the instrument, red arrows are illuminated showing which
position switches are not being activated. The unit will also issue these prompts
verbally if equipped with the optional voice annunciator.
Once the user is correctly positioned, counting begins. A clock on the position
display panel counts down the seconds remaining until counting is complete. If
the user moves out of position before the measurement is finished, the clock is
stopped until a satisfactory position is again assumed.
If mid-cycle results are enabled (an instrument setup option) contamination
detected in the first counting position will be displayed at this time. The ALARM
ACK key must be pressed to resume operation if alarms are displayed.
Position display number two is then active, and the user is instructed to enter the
second counting position. As shown on the position display, this requires facing
out from the detectors and again looking to the right (toward the active position
display panel). As before, red arrows on the position display panel indicate open
position sensors. This second count cycle is performed in a manner similar to the
first. Again, time remaining is counted down on the position display panel clock.
Alarms, if any, resulting from both count cycles are displayed graphically on the
CRT. An example of a typical alarm display appears at the end of this section.
A display of hand probe readings on the alarm information screen results when
the hand probe is removed from its cradle on the side of the instrument. This
display disappears when the hand probe is again replaced into its cradle. An
audible alarm also sounds; this may be cancelled by pressing the ALARM ACK
button. If no radiation has been detected, the user is instructed to exit the unit.
Measurement results are printed and/or stored for host computer retrieval if the
instrument is so configured.
Microprocessors are used at all levels within the PCM-2, from the main system
controller down to individual detector modules. There are virtually no switches,
jumpers or potentiometers for the technician to set or adjust. This design brings
together all system parameters, from detector thresholds and high voltage settings
to count mode selection, in a single powerful user interface.
Unavoidably, this also creates a situation in which a single incorrect keyboard
entry can change the operation of the entire instrument. In order to prevent
accidental changes, it is strongly recommended that the high-level system
password be used ONLY when it is necessary to change parameters. The
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PCM2.MAN/ Rev A/April 1995