E3 13 DTR.SG...05
(ENG)
6. TECHNICAL DESCRIPTION
6.1. Principles of Operation
The hydrostatic level probes work by converting changes in the resistance of a piezoresistive bridge, which
are proportional to the pressure (of a hydrostatic column of liquid), into a standard current output signal.
The active sensing device is a silicon diaphragm with in-diffused piezoresistors.
6.2. Construction
6.2.1.
The probe is composed of the active sensing device with silicon and sealing diaphragm, and plate with
the electronic components.
The
SGE-25S.SMART and SGE-25S
probes are additionally fitted with a diaphragm seal enabling measuring
the depth of dense media and media with suspended matter and impurities, such as liquid waste (fig. 1, 3).
The output signal is passed through a special cable with a capillary used to connect the negative side of
the measuring diaphragm to the atmosphere.
6.2.2
. Special versions of the probes can be produced with cables shielded by an additional teflon layer.
The shield covers the parts of the cable while is immersed in the medium being measured, as well as
a necessary additional segment.
The Teflon shield (in Ex version) is additional equipped in stainless steel cord escorted electrostatic charges
(see fig. 5).
6.2.3
. The probes are fitted with elements ensuri
ng excess voltage protection: „transil” diodes between the
wires, and plasma surge arresters between the wires and the casing.
The plasma surge arresters are assembled in normal and "Version SA" only.
6.3. Electronic circuit of the probes
Electronic circuit can be produced in two versions:
6.3.1.
The digital version (
SGE-25.SMART and SGE-25S.SMART probes
).
The electronic circuit changes the signal from the sensing module into digital signal and input to
a
microprocessor, which controls the probe’s operation. Using data input during the production process,
the processor processes the conversion curve, adjusts for thermal errors and carries out linearization.
After processing, the digital signal is again converted into an analogue 4÷20mA current signal, with
a superimposed digital communication HART signal.
6.3.2.
The analog version (
SGE-25, SGE-25S, SGE-25C
and
SGE-16 probes).
The electronic circuit changes the signal from the sensing module
into an output signal 4...20 mA.
The electronic circuit is equipped in filter elements assured resistance on conducted and radiated disturbances
and electric impulse.
7. PLACE OF INSTALLATION
7.1.
The level probes installed in places where liquid levels are measured in wells, tanks, boreholes etc. The
probe is immersed in the medium being measured. A special cable extends above the level of the medium;
this can be connected directly to another device or to a terminal box.
7.2. High and Low Ambient Temperatures and Medium Temperatures
When measuring liquids whose solidification point is above the ambient temperature, the medium should not
be allowed to freeze around the probe, this applies in particular to water in the case of open-air installations.
For maximum medium temperatures see sect. 5.
Data for versions Ex in accordance with Appendix Ex.03
,
Appendix Ex.04.
Содержание SGE-16
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