User manual

Model: 2100 &2300 Series
2100UM22.DOC Rev: 2.2
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2.0 INSTALLATION
NOTE: If any damage to the instrument is found, please notify an Arjay Engineering
representative as soon as possible prior to installation.
2.1 PROBES
Capacitance probes may be selected from a variety of styles for use with liquids, liquid interfaces,
and granular materials. The probe length is customer specified for the height of material desired to
be measured. Usually Teflon coated probes are used.
2.2 PROBE INSTALLATION
Standard probe entry into a tank is via a 3/4" NPT opening (standard probes) or 1" NPT opening
(heavy duty probes). Flanges and concentric shields are available as options. The entrance
configuration may vary depending on the application requirements.
TO SCREW IN PROBE (THREADED ENTRY) USE WRENCH ON LOWER HEX. The probe fittings
are compression type with Teflon ferrules assembled by applying torque between the two hex
sections. The fittings are sealed at the factory to provide a compression seal capable of withstanding
high pressures. Once opened they cannot be reassembled without new ferrules.
The probe should be mounted vertically and parallel to a reference ground surface, which is typically
the vertical wall of the tank or a concentric shield around the probe. The following points are
important when installing the probe:
1- Reference ground: This is VERY IMPORTANT and is typically the metal walls of the tank.
For non-metallic tanks, a concentrically shielded probe is required in which case the shield
provides its own Ground. IMPORTANT: For standard threaded entry and flange entry probes
(without concentric shields), make sure the fittings are clean to ensure a GOOD
ELECTRICAL CONNECTION BETWEEN THE PROBE HEAD ENCLOSURE AND THE
TANK (REFERENCE GND).
2- The distance between the probe and the ground reference:
This only applies to probes without concentric shields. The closer the distance to the tank
wall, the greater the sensitivity of measurement; too close and bridging problems may occur.
3- The degree of parallelism between the probe and the reference ground:
The probe must be parallel to the reference ground for a linear output signal. Note: that the
concentric shield option is inherently linear due to the concentric shield.
4- The measurement accuracy can be affected by the temperature change
of the material
in the tank. The amount of measurement error depends on the material. If the temperature
change is excessive, temperature correction may be required. Contact the Arjay
representative for more information.
5- Agitators or moving objects in the tank:
Moving objects in the tank close to the probe such as agitator blades, moving baffles etc.
appear as moving ground references to a capacitance probe and will cause measurement
errors. In applications where these objects are present, a concentrically shielded probe must
be used.