Panametrics DigitalFlow GC868, Руководство по обслуживанию, Страница: 33 / 64

DigitalFlow™ GC868 Service Manual (1 and 2-Channel) 3-4
Chapter 3. Diagnostics
3.3 Diagnostic
Record
Upon leaving the
Diagnostic Menu
via the [EXIT] key or the EXIT option on the option
bar, the display screen will continue to show the last diagnostic parameter that was
selected. To return to normal measurement mode, select a channel to display (for a
2-Channel meter only) and then select the desired display parameter. See Chapter
3,
Operation
, of the
Startup Guide
for detailed instructions.
The values for the diagnostic parameters immediately after initial installation of the
meter and verification of proper operation should be entered in Table A-2 on page
A-3 . These values can then be compared to future values to help diagnose any
future malfunction of the system.
3.4 Flowcell
Problems
If preliminary troubleshooting with the
Error Code Messages
and/or the
Diagnostic
Menu
indicates a possible flowcell problem, proceed with this section. Flowcell
problems fall into two categories:
• gas problems
• pipe problems.
Read the following sections carefully to determine if the problem is indeed related to
the flowcell. If the instructions in this section fail to resolve the problem, contact the
factory for assistance.
3.4.1 Gas Problems
Most gas-related problems result from a failure to observe the flowmeter system
installation instructions, as described in the
Startup Guide
. Refer to Chapter 1,
Installation
, of the
Startup Guide
to correct any installation problems.
If the physical installation of the system meets the recommended specifications, it is
possible that the gas itself may be preventing accurate flow rate measurements.
The gas being measured must meet the following requirements:
1.
The gas must be homogeneous, single-phase and relatively clean.
Although a
low level of entrained particles may have little effect on the operation of the
Model GC868, excessive amounts of solid or liquid particles will absorb or
disperse the ultrasound signals. This interference with the ultrasound
transmissions through the gas will cause inaccurate flow rate measurements. In
addition, temperature gradients in the gas flow may result in erratic or
inaccurate flow rate readings.
2. The gas must not excessively attenuate ultrasound signals.
Some gases (i.e., high-purity carbon dioxide, hydrogen, etc.) readily absorb
ultrasound energy. In such a case, an E1 error code message will appear on the
display screen to indicate that the ultrasonic signal strength is insufficient for
reliable measurements.
3.
The gas sound speed must not vary excessively.
The Model GC868 will tolerate relatively large changes in the gas sound speed,
as may be caused by variations in gas composition and/or temperature.
However, such changes must occur slowly. Rapid fluctuations in the gas sound
speed, to a value that is considerably different from that programmed into the
Model GC868, will result in erratic or inaccurate flow rate readings. Refer to
Chapter 2,
Initial Setup
, of the
Startup Guide
and make sure that the appropriate
sound speed is programmed into the meter.