705-5100-111 Datasheet, PDF (2/28 Pages) Magnetrol International, Inc. – Eclipse® Enhanced Model 705 Guided Wave Radar Level Transmitter

TECHNOLOGY
OVERALL LEVEL
Eclipse Guided Wave Radar is based upon the technolo-
gy of TDR (Time Domain Reflectometry). TDR utilizes
pulses of electromagnetic energy transmitted down a
wave guide (probe). When a pulse reaches a liquid sur-
face that has a higher dielectric constant than the air (ε_r
of 1) in which it is traveling, the pulse is reflected. The
transit time of the pulse is then measured via ultra speed
timing circuitry that provides an accurate measure of the
liquid level.
INTERFACE LEVEL
The Eclipse Model 705 is capable of measuring both an
upper liquid level and an interface liquid level. Even after
the pulse is reflected from the upper surface, some of the
energy continues down the GWR probe through the
upper liquid. The pulse is again reflected when it reach-
es the higher dielectric lower liquid. It is required that the
upper liquid has a dielectric constant between 1.4 and 5,
and the lower liquid has a dielectric constant greater than
15. A typical application would be oil over water, with
the upper layer of oil being non-conductive (ε_r ≈ 2.0),
and the lower layer of water being very conductive
(ε_r ≈ 80). The thickness of the upper layer must be > 2"
(50 mm). The maximum upper layer is limited to the
length of the GWR probe, which is available in lengths
up to 40 feet (12 meters).
EMULSION LAYERS
As emulsion layers can decrease the strength of the
reflected signal, the Eclipse Model 705 should only be
utilized in those interface applications that have clean,
distinct layers. Contact factory for application assistance.
Reflected
Pulse
Initial
Pulse
Air ε_r = 1
Liquid ε_r > 1.4
for coaxial probes
Transmitted
Pulse
Overall Liquid Level
Reference
signal
Air ε_r = 1
Upper level
signal
Interface
level signal
> 2"
(50 mm)
< 2" (50 mm)
Low dielectric medium
(eg. oil, ε_r = 2)
high dielectric medium
(eg. water, ε_r = 80)
Time
Interface Level
Reflected
Pulse
Initial
Pulse
Air ε_r = 1
ε_r > 1.9 for twin
flexible probes
Transmitted
Pulse
Bulk Solid Level
2