Yokogawa AC8 Calibration Units - Manual (Page 12)

12
IM 11M6D2-02E-A
3) If the calibration interval is shorter than the sum of the
stabilization time plus calibration time, the second calibra-
tion start time will conflict with the first calibration. In such a
case, the second calibration will not be conducted. (When
both zero and span calibrations are to be performed, the
calibration time is double that required for a single (zero or
span) calibration).
4) If the (Calibration) Interval is et to DD: 00, HH: 00 then
auto Calibration will not be performed.
5) If the start date is set before the current date, then Auto
Calibration will not start.
6) [Cal. Time] of [Calibration timing] display will be equalized
to [Check time] of [Semi-auto ind. Chk] display
other
commands Purging
the
channel
Man. Cal.
SemiAuto
AutoCal X
X
Wait
X
X
Wait
X
X
Wait
X
X
Wait
X: Cannot perform calibration
Wait: Wait until other command finishes before starting calibration
X
X
Wait
X
X
X X
X
X X
X
X
Other
channel
CAL
Indication
check in
other channel
Blowback in
other
channel
Maintenance CAL chan.
in warmup
status
CAL chan.
in ERR
status
CAL chan.
now
disabled
Table 7.1 When Auto Calibration conflict with Other Commands
VIII. MAINTENANCE
Because of the AC4/AC8 unit’s simplified construction, no
routine maintenance is required, other than replacing the
calibration gas when necessary. When cal gas cylinders are
changed refer back to Section 7.1.2 Calibration Setup Pro-
cedure. Failure to perform the Calibration Setup Procedure
upon replacing cal gases will result in an error in the zero
correction values. When changing gases it is also necessary
to check the zero gas flow rate.
It is recommended that periodic inspections are performed
to insure a sufficient supply of calibration gases when the
pressure switch input is not used. Also, periodic checks
verify that the flow rate of the calibration gases, to the indi-
vidual oxygen detector probes have not been accidentally
changed. It is important that the zero gases flow at a rate of
0.6 LPM (600mL/min.), while the reference air (instrument air)
flows at 0.8 LPM (800mL/min).
Refer to Section 10 of this manual for a listing of spare parts
for the AC4/AC8.
IX. TROUBLESHOOTING
9.1 TYPICAL CALIBRATION PROBLEMS
1) Gas does not flow to the probe.
• If reference air is used, then the reference air flow meters
should show 0.8 LPM at all times. If the reference air flow
meters do not show 0.8 LPM, then confirm that the instru-
ment air has been turned on by checking the regulator gauge
(10to 35 psi).
• Confirm override screws are in the NORMAL mode for the
block solenoid and all channel solenoids.
• Turn block solenoid to the manual position. Cal gas flow
meter should show 0.6 LPM. If cal gas flow meter shows 0
LPM, turn the black knob on the flow meter to open the flow
meter. Set flow rates for all probes as according to proce-
dures shown in Section 5 of this manual.
2) Flow meter will not go to 0.8 LPM for reference air.
• Turn the flow rate adjustment knob only, NOT the override
screw.
• Only one channel should be in the manual override posi-
tion. All other probes should be in the normal position.
• Check the pressure regulator at the gas source. If the
pressure is below 14 psi, increase pressure in increments
of 5 psi, and adjust reference flow meters. DO NOT in-
crease pressure to greater than 35 psi. If more than 35 psi
is needed, attempt to move the calibration box closer to the
probes, without compromising safety or the ambient operat-
ing temperature of the auto cal unit.
• Tubing outside diameter (O.D.) should not be greater than
1/4” .Tubing runs should not be in a T position, and should
remain separate for each probe.
• Check for leaks at compression fittings. All NPT fittings
should have Teflon tape on the threads to prevent leaks.
3) Flow meter will not go up to 0.6 LPM for cal gas.
• Same solution as above, except make adjustment to the
cal gas flow meter.
4) Wrong gas flowing to the probe.
• Confirm that gases are plumbed correctly at the left side of
the calibration unit.
• Turn the override screw on the three-way solenoid to the
normal position.
• Perform a cal check in semi auto calibration mode. (See
Section 5).
IMPORTANT
When performing an actual automatic or semi automatic cali-
bration, and a calibration alarm occurs, it is necessary to reset
the channel. Instead, recalibrate the channel to remove the cali-
bration alarm. For additional troubleshooting procedures, refer
to the AV550G manual, Section 12.