Instruction manual –HBLC-xxx –Levelsensor (005-UK) 4 / 11
WE INCREASE
UPTIME AND EFFICIENCY
IN THE REFRIGERATION INDUSTRY
Introduction
HBLC-XXX is an intelligent sensor with a built-in
microprocessor. It is designed for continuous
level measurement of liquid CO2 or HFC
refrigerant in refrigeration systems.
The sensor emits a 4-20mA analogue signal,
which is proportional to the liquid level.
The construction of the sensor makes it suitable
for systems with pressure of up to 150 bar.
Measurement Principle
The sensor is a capacitive sensor. The capacitive measurement principle is based on the electrical
properties in the proximity of a capacitor. A capacitor is an electrical component that is capable of building
and sustaining an electrical charge.
A capacitor basically consists of two plates.
When a charge is applied to a plate, the other
plate will be charged with the opposite polarity
and retain the charge until it has been grounded.
The magnitude of the charge (the capacitance)
that can be generated depends, among other
things, on what is found between the plates.
The substance between the plates is referred to
as a dielectric.
Rather than the two plates, the sensor for level
measurement is shaped as a cylindrical rod.
When liquid covers the sensor, the measured
capacity is changed.
The conductivity of a material can vary depending
on temperature, chemical composition, and the
homogeneity of the material, and therefore it can
in some cases require a different factory
calibration.
HB Products sensors are calibrated so that they differentiate between conductive and non-conductive
liquids.
In refrigeration systems, oil, HFC and liquid CO2 are not regarded as conductive fluids, whereas refrigerants
such as ammonia and brine are regarded as conductive.
Design and Function
The sensor consists of a mechanical part and an electronic part. These are easily separated by loosening 2
grub screws or, for housings with mounting tabs, by pressing the sensor in towards the mechanical part and
turning the housing counter-clockwise until a wave washer pushes it from the mounted position. The
electronic part is designed in accordance with the IP65 waterproof rating and so as to resist vibrations.
The mechanical part is produced in AISI304/PTFE and tested to withstand high pressure.
The sensor is a very accurate analogue level transmitter for continuous measurement of liquid CO2 or HFC
on refrigerant plants. Additionally it may serve as high level switch, since the in-built switch function gives
an alarm signal at the 100% level.
