Teledyne 200E, Инструкция по эксплуатации, Страница: 219 / 302

Troubleshooting & Repair Model 200E Instruction Manual
Check the power supply to the valve (12 V to the valve should turn on and off when
measured with a voltmeter).
Note that 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.
• Another reason for high (although not necessarily out-of-range) values for AutoZero
could be the ozone air filter cartridge, if its contents has been exhausted and needs
to be replaced. This filter cartridge (Figure 3-2) filters chemicals that can cause
chemiluminescence and, if saturated, these chemicals can break through to the
reaction cell, causing an erroneously high AutoZero value (background noise).
• A dirty reaction cell can cause high AutoZero values. Clean the reaction cell
according to Section 9.3.9.
• Finally, a high HVPS voltage value may cause excess background noise and a high
AZero value. The HVPS value changes from analyzer to analyzer and could show
nominal values between 450 and 800 V. Check the low-level hardware calibration of
the preamplifier board and, if necessary, recalibrate exactly as described in Section
11.6.5 in order to minimize the
HVPS .
11.5. Subsystem Checkout
The preceding sections of this manual discussed a variety of methods for identifying
possible sources of failures or performance problems within the analyzer. In most cases this
included a list of possible causes and, in some cases, quick solutions or at least a pointer to
the appropriate sections describing them. This section describes how to determine if a
certain component or subsystem is actually the cause of the problem being investigated.
11.5.1. Simple Vacuum Leak and Pump Check
Leaks are the most common cause of analyzer malfunction; This section presents a simple
leak check, whereas Section 11.5.2 details a more thorough procedure. The method
described here is easy, fast and detects, but does not locate, most leaks. It also verifies the
sample pump condition.
• Turn the analyzer ON, and allow at least 30 minutes for flows to stabilize.
• Cap the sample inlet port (cap must be wrench-tight).
• After several minutes, when the pressures have stabilized, note the SAMP (sample
pressure) and the RCEL (vacuum pressure) readings.
• If both readings are equal to within 10% and less than 10 in-Hg-A, the instrument is
free of large leaks. It is still possible that the instrument has minor leaks.
• If both readings are < 10 in-Hg-A, the pump is in good condition. A new pump will
create a pressure reading of about 4 in-Hg-A (at sea level).
11.5.2. Detailed Pressure Leak Check
If a leak cannot be located by the above procedure, obtain a leak checker similar to T-API
part number 01960, which contains a small pump, shut-off valve, and pressure gauge to
create both over-pressure and vacuum. Alternatively, a tank of pressurized gas, with the
two stage regulator adjusted to ≤ 15 psi, a shutoff valve and pressure gauge may be used.
204 044100102 Rev A