Teledyne T200, Руководство по эксплуатации, Страница: 249 / 425

Teledyne API
– T200 NO/NO
2
/NO
X
Analyzer Operation Manual Troubleshooting & Service
247

Leaking NO/NO
X
valve. Carry out a leak check.

Dirty or plugged critical flow orifices. Check flows, pressures and, if necessary,
change orifices (Section 11.3.10).

Wrong materials in contact with sample - use glass, stainless steel or Teflon
materials only. Porous materials, in particular, will cause memory effects and slow
changes in response.

Dirty reaction cell. Clean the reaction cell.

Insufficient time allowed for purging of lines upstream of the analyzer. Wait until
stability is low.

Insufficient time allowed for NO or NO
2
calibration gas source to become stable.
Wait until stability is low.

NO
2
converter temperature is too low. Check for proper temperature.
12.6.3. AUTO ZERO WARNINGS
Auto Zero warnings occur if the signal measured during an Auto Zero cycle is higher
than 200 mV.
Note
The Auto-Zero warning displays the value of the Auto Zero reading when the
warning occurs.

If this value is higher than 150 mV, check that the Auto Zero valve is operating
properly.

To do so, use the
SIGNAL I/O
functions in the
DIAG
menu to toggle the valve
on and off.

Listen if the valve is switching, see if the respective LED on the relay board is
indicating functionality.

Scroll the
TST
functions until
PMT
is displayed and observe the PMT value change
between the two valve states.

If the valve is operating properly, you should be able to hear it switch (once a
minute under normal operation or when manually activated from the
SIGNAL
I/O
menu):

the PMT value should drop from span gas reading (e.g., 800-900 mV at
400 ppb NO) to less than 150 mV and;

the LED on the relay board should light up when the valve is activated.

If the PMT value drops significantly but not to less than 150 mV, the valve is
probably leaking across its ports.

In this case, replace the valve.

If the PMT value does not change at all, the valve is probably not switching at
all.

Check the power supply to the valve (12 V to the valve should turn on and
off when measured with a voltmeter).
Note
It takes only a small leak across the ports of the valve to show excessive Auto
Zero values when supplying high concentrations of span gas.
06858E DCN7057