ENMET
Corporation
ISA-40 Oxygen Monitor
14
c)
Adjust the appropriate meter gain potentiometer, shown below, so the channel's meter reads full scale (26%
oxygen on most meters). Adjust this pot. Counterclockwise to increase, clockwise to decrease meter reading.
Channel
Potentiometer
On Circuit Board
1
R110
For channel(s) 1 (and 2)
2
R210
For channels 1 and 2
3
R110
For channel(s) 3 (and 4)
4
R210
For channels 3 and 4
d)
Remove the voltmeter leads from the test points.
4.
Alarm Set Adjust:
a)
Adjust the oxygen gain potentiometer for the particular channel until the meter reads at the appropriate alarm
point (usually 18.0%).
b)
Adjust the appropriate alarm point adjust potentiometer, indicated below, counterclockwise until the oxygen
circuit just barely goes into alarm. The red oxygen deficiency lamp should just activate as you adjust this
potentiometer. If lamp is on before the potentiometer adjustment, adjust this potentiometer clockwise until the
lamp is off, then readjust counterclockwise until the lamp just barely activates:
Channel
Potentiometer
On Circuit Board
1
R116
For channel(s) 1 (and 2)
2
R216
For channels 1 and 2
3
R116
For channel(s) 3 (and 4)
4
R216
For channels 3 and 4
c)
Using the oxygen gain potentiometer on the front of the control unit for the channel you are working on, adjust
the channel's oxygen meter up so that the channel comes out of alarm. Then adjust down again slowly until to
verify that the unit goes into alarm.
d)
Expose the channel's oxygen cell to clean, fresh air for 5 minutes. Using the oxygen gain potentiometer, adjust
the meter to read 20.9%.
W
ARNING
:
The oxygen sensor
Must
be in clean, fresh air for this adjustment. If there is any possibility that oxygen
deficient air is near the sensor, supply bottled 20.9% by volume oxygen to the sensor for a couple of
minutes, then adjust gain.
e)
If possible, exhale all your breath over the oxygen cell. The meter reading should drop and the oxygen alarm
should come on at the predetermined alarm point (usually 18.0% oxygen by volume).
f)
If the oxygen alarm does not come on at this point, repeat the entire procedure checking terminal connections,
test points, and voltage settings very carefully. If it still does not alarm, contact your local authorized
ENMET
service center.
5.
The oxygen circuit alignment is now complete.
5.4 Circuit Breakers / Fuse
ISA-40
instruments above serial number 2568 are equipped with two circuit breakers and a fuse in the
AC
power
supply wiring. The circuit breakers are rated at 1 amp, and the fuse is rated at 50 milliamps (slow blow).
When the fuse or a circuit breaker opens the circuit, the power supply to the
ISA-40
is interrupted. All lamps on the
front of the instrument are off. First, check to see if one or both circuit breakers have released their reset button. If so,
press in the reset button. If not, visually check the fuse for a broken element, then test the fuse electrically for
continuity. If the fuse element is broken (visual indication) or cracked (electrical indication), replace it with the same
fuse (see section 7.1 for part number). If, after resetting a circuit breaker or replacing the fuse, the same component
opens the circuit again within a short period of time, do not attempt to reset or replace the component again; have the
instrument and power supply inspected to determine the source of the overload.
C
AUTION
:
The fuse for the
ISA-40
is a "slow blow" fuse. If this fuse requires replacement, the exact replacement is
required (see section 7.1 for part number). Any other type voids the electrical certification. Note also that if the
replacement fuse is not a "slow blow" fuse, the replacement fuse will blow as soon as the instrument is supplied
with power.