PCM-2 Manual.pdf - Voss Associates

the close proximity of the beam to the front detector panel establish a sensing
geometry which forces beam interrupt (upper body position sensing) by the user's
head and/or shoulders and accomodates a wide range of user statures. PCM-2
instruments equipped with this option are set-up to initiate and continue either of
its count cycles only if the full compliment of mechanical body position switches
and this additional photocell "torso" switch are actuatedlinterrupted. An
additional voice command, to prompt proper torso positioning, is included with
this option when accompanied by the Voice Annunciator Option (PCM2 OPT2).
Therefore, in conjunction with the unit's standard mechanical proximity switches,
this additional photocell serves to establish and confirm total body positioning in
close proximity to the detectors. This option is thereby recommended for
customers with relatively sensitive monitoring needs such as alpha contamination
measurement.
System Adjustments
Maintenance of the factory system adjustments is critical in keeping the head and
shoulders position sensor functioning properly. No routine realignments of the
photocell emitter/receiver pair are required for this option. However, periodic
photocell realignment may be necessary if the instrument is subject to inordinate
amounts of shock or vibration (i.e. due to excessive moving over rough surfaces,
or general rough handling and/ or usage of the instrument).
As long as the photocells are communicating with each other in a repeatable
manner, they can reliably detect the intended head and shoulders proximity of a
user. This critical communication link is established by the angular alignment of
the photocell pair which is fixed at the emitter housing on the front detector panel
and adjustable at the receiver on its mounting bracket within the PCM-2 ceiling
assembly. If it is determined that there is no intercommunication between the
photocells, and the photocell electronics are operational, then realignment of the
photocell receiver is necessary to restore the proximity sensing function.
The photocell receiver's mounting bracket is slotted to allow both positional and
angular alignment adjustments of the photocell. Loosen the screws in either
adjustment plane and make slight rotaton and/or position adjustments to the
reciever photocell as necessary to reestablish communication with the emitter
photocell. A good communication link between the two will be evidenced by the
illuminated LED on the modulated amplifier within the upper electronics
enclosure. The pulse of the LED will be more evident for a "weak" photocell
link and less evident or even constant for a good strong photocell link. A
functionally strong link between the photocells will be repeatably reestablished
after the photocell beam is repeatedly broken. Note that two persons may be
required to facilitate these sensitive adjustments. Once functionally readjusted, the
reciever photocell's mounting fasteners can again be tightened. Recheck the
reliability of the photocell link after fixing the receiver photocell in place as
tightning of its mounting fasteners can change the adjustment.
PCM2.MAN/ REV Ai Aprii 1995 17-91