Fluke Biomedical 875 Victoreen - Manual (Page 22)

Function Description
Functional Description
4
4-1
n
ch about four
h
e
he posts keep the disks separated so they do not come in contact, and
ch diameter housing which contacts only the neutral
d
d with a mixture of helium (2%) and nitrogen at atmospheric pressure and
d
le 876A-1
ing signals
een printed circuit boards. In addition, drawing
Section 4
Function Descriptio
4.1 Functional Description
High-Range Containment Monitor Detector 877-1
The high-range containment monitor detector is an ion chamber detector that has the appearance of a
six-inch diameter domed cylinder about seven inches long, mounted on an L shaped bracket. Inside the
cylinder are two flange-mounted electrodes consisting of 31 flat, disk-shaped plates, ea
inches in diameter, stacked, and mounted on disk rods. The 31 disks form two groups, interleaved wit
each other, 16 collection disks and 15 signal disks. Because of the interleaving, they appear as only on
stack, but the collection disks are mounted on three collection disk-posts and the signal disks on three
signal disk-posts. Spacers on t
clearance holes in the disks allow posts of the opposite polarity to pass through without contact. The
assembly has the appearance of a large air capacitor. The mounting posts are attached to the mounting
flange through insulating spacers, so the flange and housing will be neutral with respect to the charges
applied to the electrodes. The collecting diskposts are elongated beyond the last collecting disk to support
a cup-shaped liner having the same potential as the collecting disks, thus becoming part of the collector.
The whole assembly is covered by the six-in
mounting flange. The mounting flange is pierced by three holes. One hole supports the exhaust tube use
for exhausting and back filling the chamber. The other two support two 2-pin connectors, one for each
electrode. One pin in each pair is connected to the neutral mounting flange. When the coaxial signal
cable is connected to this connector, the cable shield is connected to the neutral pin.
The entire chamber is fille
sealed.
CAUTION
The seal on this chamber must not be broken. To
do so would alter the calibration and specifie
energy response of the system.
4.2 Readout Modu
NOTE
Drawings 876A-1-3H and 876-1-3A serve as
interconnecting diagrams for trac
betw
876-1-3A contains the main power supply