Fluke Biomedical 875 Victoreen - Manual (Page 28)

Function Description
Readout Module876A-1
4
4-7
Circuit Actions at Manual and Automatic Initiation of ECS Test
d to
ly
with a 0.976
illisecond repetition rate. It is followed by counters U204 and U205. The action of U204 is entirely
stricted may be
pen-cir s
eration and
onitori
nction
test and;
) re-initiation rator
adverte use the
stant of ECS button
itiates t 5 pin 6
the latc ; 2) pin 5, U207
nput); 3) pin rator
205. Th
xplanati
ow Vol
he elem
ssociated ca
t the arr
uickly to rging
apacito ntiometer
227, ramp v rate of
harge of cap tor plates.
he ra only 6.2
olts. Fro d circuit
oard, wh scription of
e power supply printed circuit board.
NOTE
During the ECS test, all alarms are muted; that is,
their operation is disabled until the completion of
the test. During this six-second period there is no
warning of a high radiation condition. If this
situation is not tolerable, two containment monitors
must be installed.
Action of Green Safe/Reset Light and Alarm During ECS Test
The behavior of the green SAFE/RESET panel light during the test is as follows:
A pass condition is indicated by the green light remaining lighted throughout the test.
A fail condition is indicated if the green light goes out at the end of the test.
Whether the ECS test is initiated automatically or at the will of the operator, a trigger signal is delivere
pin 4 (manual) or pin 5 (automatic) of U206, whose output initiates the low voltage ramp generation.
Automatic operation may be disabled by the removal of jumper 200A. The system will then respond on
to the pressing of the ECS button.
The circuit containing U201 (pins 5, 6, 7) and U208 (pins 11 and 12) constitutes a clock
m
re
to automatic control of the ECS test, as is the output from pin 1 of U205 (note that it
cuited by the removal of jumper 200A). However, the outputs from pins 3, 5, and 6 have function
both manual and automatic action. In addition, they involve both the ramp-gen
ng functions of the ECS board, and also enter into the operation of two important auxiliary
s: 1) generation of a muting pulse, so that the alarms will not be set off during the ECS
prevention--that is the prevention of malfunction on manual operation in case the ope
ntly presses the ECS button more than once. The monitoring function is involved beca
generation of the latch-enable pulse occurs a precise time after the pressing of the
he test (toward the end of the test, when conditions have stabilized). The path from U20
h-enable generator may be seen to involve the following points: 1) pin 10, U203
6, U207 (output) and finally pin 11, U207, whose output drives the latch-enable gene
e latch and latch enable functions will be explained with the monitoring circuits after the
on of the ramp generation.
tage Ramp Generator
ents that enter the generation of the low voltage ramp are U203, U208, U201, Q204, and
pacitors, resistors, and diodes. U203 is an auxiliary element.
ival of the trigger, Q204 serves the purpose of reducing the voltage previously at terminal 5
zero, at which instant the ramp-generator proper takes over. Basically, C210 is the cha
r, and the other components serve either as charging resistors or linear elements. Pote
oltage per second adjustment (RAMP V/SEC ADJUST), serves to determine the
acitor C210, and consequently, the rate of rise of the voltage applied to the detec
mp that is generated by the ramp generator appears at terminal 5, where its maximum is
m terminal 5, it is connected to the high voltage generator on the power supply printe
ere it controls the generation of the high voltage, as explained in the functional de
o
that enter into
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