805-501A-111 Datasheet, PDF (20/36 Pages) Magnetrol International, Inc. – KOTRON® MODEL 805 SMART RF LEVEL TRANSMITTER

Air
Non-conductive
(insulating)
medium
Figure B
Bare
metal
probe
Metal
tank wall
(ground
reference)
Capacitance is measured in Farads. The value we utilize in
industrial measurement is an extremely small unit called a
pico Farad (pF). A pico Farad is one trillionth of a Farad
(10^-12).
Capacitance value increases as the dielectric increases,
the plate size increases, or the distance between the
plates decreases.
In industrial applications (Figure B), the probe is one plate
of the capacitor, the tank wall is the other plate (ground
reference). The insulating material that separates them is
the dielectric. A tank that is empty is actually filled with
air that has a dielectric of 1, the baseline of the dielectric
scale. All materials have a dielectric higher than air, e.g.
oil = 2.5, alcohol = 18, tap water = 80, etc. As a tank is
filled with media, the air (dielectric = 1) is being displaced
by the media having a higher dielectric; consequently, the
amount of capacitance being generated between the probe
and the tank wall increases.
3.3 Troubleshooting
The Model 805 transmitter is designed and built for
trouble-free operation over a wide range of operating con-
ditions. Common transmitter problems are discussed in
terms of their symptoms and recommended corrective
actions. In addition, information on how to handle mater-
ial build-up on the probe is provided in this section.
WARNING! Explosion hazard. Do not connect or disconnect
equipment unless power has been switched off or the
area is known to be safe.
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50-660 Kotron Model 805 Smart RF Level Transmitter