Converter – Teledyne 9110E - Nitrogen Oxides Analyzer User Manual

Page 232

Troubleshooting & Repair

Model 9110E Instruction Manual

218

M9110E Rev B

11.5.15.3. Ozone Flow

Measure the voltage across TP1 and TP3. With proper ozone flow (80 cm³/min at the ozone

dryer inlet), this should be approximately 2.0 ± 0.2 V (this voltage will vary with altitude).
With flow stopped (pump turned off), the voltage should be approximately 0 V. If the

voltage is incorrect, the flow sensor or the board may be faulty. A cross-leak to vacuum

inside the Perma Pure dryer may also cause this flow to increase significantly, and the

voltage will increase accordingly. Also, make sure that the gas flows from P1 to P2 as

labeled on the flow sensor (“high” pressure P1 to “low” pressure P2 or “Port” 1 to “Port” 2).

11.5.16. NO

Converter

The NO

converter assembly can fail in two ways, an electrical failure of the band heater

and/or the thermocouple control circuit and a performance failure of the converter itself.

1) NO

converter heater failures can be divided into two possible problems:

• Temperature is reported properly but heater does not heat to full temperature. In

this case, the heater is either disconnected or broken or the power relay is broken.
• Disconnect the heater cable coming from the relay board and measure the

resistance between any two of the three heater leads with a multi-meter. The

resistance between A and B should be about 1000 Ω and that between A and C
should be the same as between B and C, about 500 Ω each. If any of these

resistances is near zero or without continuity, the heater is broken.

• Temperature reports zero or overload (near 500° C). This indicates a disconnected

or failing thermocouple or a failure of the thermocouple circuit.
• First, check that the thermocouple is connected properly and the wire does not

show signs of a broken or kinked pathway. If it appears to be properly

connected, disconnect the yellow thermocouple plug (marked K) from the relay
board and measure the voltage (not resistance) between the two leads with a

multi-meter capable of measuring in the low mV range. The voltage should be

about 12 mV (ignore the sign) at 315° C and about 0 mV at room temperature.

• Measure the continuity with an Ohm-meter. It should read close to zero Ω. If the

thermocouple does not have continuity, it is broken. If it reads zero voltage at

elevated temperatures, it is broken. To test the thermocouple at room tempera-

ture, heat up the converter can (e.g., with a heat gun) and see if the voltage

across the thermocouple leads changes. If the thermocouple is working properly,

the electronic circuit is broken. In both cases, consult the factory.

2) If the converter appears to have performance problems (conversion efficiency is outside

of allowed range of 96-102%), check the following:

• Conversion efficiency setting in the CAL menu. If this value is different from 1.000,

this correction needs to be considered. Section 7.1.7 describes this parameter in

detail.

• Accuracy of NO

source (GPT or gas tank standard). NO

gas standards are typically

certified to only ±2% and often change in concentrations over time. You should get

the standard re-certified every year. If you use GPT, check the accuracy of the ozone
source.

• Age of the converter. The NO

converter has a limited operating life and may need to

be replaced every ~3 years or when necessary (e.g., earlier if used with continu-

ously high NO

concentrations). We estimate a lifetime of about 10000 ppm-hours (a