Fluke Biomedical 875 Victoreen - Manual (Page 43)

Victoreen 875 High Range Containment Monitor
Operator Manual
5-12
able 5-1. Truth Table for Pass and Fail Conditions in The Latch Circuit
(Circuit assumed initially in Pass Condition)
T
Fail Condition Pass Condition
Pin
Voltage
State
Voltage Comments Pin State Comments
4 L (low) Since 6 is H (high) 4 H Because 6 is L (also 5)
3 H (high) Since 1 & 2 are Low 3 L Because 2 is H
13 H Connected to 3 8 H Connected to 4
11 L Since 13 is H 13 L Connected to 3
9 L Connected to 11 10 L Because 8 is H
8 L 12 L Connected to 4
10 H
9, 10) is
11 H Bec
Since U202, (8,
NOR
ause 12 and 13 are L
12 H
from Lo
Result: Output switches
w to High
This is the original condition. No
change takes place.
Notes:
ition assumes 12 and 1
The truth table shows that no change in the output can occur without the presence of the enable pulse,
the monitoring signal indicat the ramp voltage
able 5-2. Signal In Fail State (High Signal Input)
Pin 1 Voltage State Comments
1) Enable pulse assumed present, so 1 and 5 are L.
2) Initial cond 0 L.
even though es a fail condition. This is necessary because
starts from zero during the ECS Test.
T
10, U208 and 6, U202 H Fail state
9, U208 and 2, U202 L After inversion
1,5, U202 H No enable input
4, 8, U202 L Because of NOR action
3, 13, U202 L Because of NOR action
10, 12, U202 L Because of NOR action
Thus the circuit does not react to a fail signal input unless pins 1 and 5 are low.
If a problem cannot be resolved by applying the
troubleshooting and maintenance procedures
provided here, please contact Fluke Biomedical at
440.248.9300 for assistance.
NOTE