Eclipse 705 Installation And Operating Manual page 28

MAINTENANCE
TROUBLESHOOTING APPLICATIONS: Level
Most frequent application problems that may occur, media
buildup on the probe and stratification, are covered here.
Media buildup on the probe is not a problem in most
cases–Eclipse circuitry typically works very effectively.
Media buildup should be viewed as two types – Film
Coating and Bridging.
Recommended guidelines to select the right GWR probe:
- Relatively clean liquids: use the standard coax GWR
probes
- Possible build up: use the enlarged coax or twin rod
GWR probe
- Extreme build up: use the single rod GWR probe
• Continuous Film Coating
The most typical of coating problems where the media
forms a continuous coating on the probe. Eclipse will
continue to measure effectively with some small degra-
dation in performance. A problem can develop if the
product begins to buildup on the spacers that separate
the probe elements. High dielectric media (e.g, water-
based) will cause the greatest error.
Continuous film coating / Bridging
TROUBLESHOOTING APPLICATIONS: Interface
It is not uncommon for interface applications to have an
emulsion layer form between the two media. This emulsion
layer may pose problems for Guided Wave Radar as it may
decrease the strength of the reflected signal. Since the
properties of this emulsion layer are difficult to quantify,
applications with emulsion layer should be avoided with
Eclipse.
28
Bridging
Film
Coating
• Bridging
Media that is viscous or solid enough to form a clog, or
bridge, between the elements causes the greatest
degradation in performance. High dielectric media (eg.
water-based) will show as level at the location of the
bridging.
• Stratification/Interface
The Eclipse transmitter is designed to measure the first
air/media interface it detects, when configured for level
measurement only. It will not measure further liquid/
liquid interfaces. However, a low dielectric over a high
dielectric application can cause a measurement problem
if the level of the low dielectric medium becomes small
enough (a few cm) to cause the electronics to trigger on
the high dielectric medium that lies beneath it. Select the
Fixed Threshold option to read the upper medium.
Example: oil over water.
Bridging
Threshold
«Fixed»
GOOD
Film
Threshold
Coating
«CFD»
WRONG
Outer tube
Inner rod
Air/gas
<
r
ε
>
r
ε
Stratification/Interface
Oil
2.0
r
ε
Emulsion
Layer
Water
80
r
ε