E6 36 DTR.APC.APR.ALW.03(ENG)
6. CONSTRUCTION
6.1. Principle of measurement. Electronic system construction
The electrical signal from the sensor which is proportional to the pressure is sent to a digital analog input and
converted to a digital signal. The digital signal is transmitted through optoelectronic galvanic barrier to
conditioning module. The main plate microcontroller reads measured values and using internal algorithms
calculates the exact value of pressure and temperature. The calculated value of the process variable is
displayed on the integrated LCD screen, which can be configured as needed. The digital value of the measured
pressure signal is converted to an analogue 4 - 20 mA signal. A built-in modem BELL 202 and HART rev5.1
communication stack enables communication with the transmitter via a converter HART/RS232 attached to
a PC and software, or via communicator. The electrical output of transmitter is equipped with a suppression
filter and surge protective elements. The block circuit of transmitter is presented at Fig 1. The APC..., APR...
transmitters monitor of the work of their hardware resources and the correctness of calculations, and inform
about mistakes by displaying a message on the LCD screen, and exposing the alarm current in the loop
(depending on configuration). Sensor electronics is galvanically separated from the measuring line. This allows
reduce a susceptibility of measurement to interference and increased safety in intrinsically safe and flameproof
applications.
6.2. Enclosure of transmitters
Enclosures of APC..., APR ... transmitters are made of die-cast aluminium alloy or stainless steel and consist of
a body and two screwed covers (display and electrical connection), one of which is equipped with a glass
window. The enclosure provides two holes on the cable entries with thread M20x1.5 or ½ NPT (the unused hole
is sealed with stopper). The housing consists of two chambers separated by an electrical culvert. Housing is
equipped with ground terminals: internal and external. The basic units of transmitter are: measuring sensor,
in which pressure signal is converted into electric signal, and electronic units, transforming signal from
measuring sensor into unified output signal.
6.3. Main electronics plate with display
Main plate electronics with display is placed in the casing of polycarbonate. It is placed in bigger from two
chambers where is possibility to change of display position by 345 with 15º increments to required position
(in "Version MID" rotation the display is possible by 180º, in ±90º) (see Fig 4). In second chamber is placed
a connecting board with protective devices and EMC filter.
6.4 Measuring head
The measuring head is a measuring unit equipped with a silicon diaphragm sensor. The sensor is placed in
a silicone oil-filled space enclosed, on one side of the culvert with the leads insulated in glass on the other side
of the separating diaphragm which separates the sensor from the medium (APR… transmitters have a two
separated diaphragms). Measuring heads are equipped with process connectors as at Fig. 6a, 7a and 8a or
other. APR… transmitters measured head has two process connectors type P or C connector (Fig. 10) for
assembly on manifold. Measuring head of APR-2000GALW is intended to low pressures of gases with
overpressure to 100kPa (or 35kPa). This transmitter in standard version (economic) is equipped in the process
connectors adjusted to elastic pipes Ø6x1, and in industrial versions in adapters as Figure 18.
6.5. Separators
For pressure measurement of viscous, chemically reactive or hot process mediums, the transmitter may be
additionally fitted with various types of diaphragm seal.
The diaphragm seal transmits the process pressure via an inert fluid fill between the diaphragm of the seal and
the diaphragm of the transmitter. When remote diaphragm seals are fitted, the pressure between the diaphragm
seal and the transmitter is via a filled capillary. The seal’s construction is dependent on the process medium
properties and the application operating conditions.
APR-2000YALW smart level probe is equipped in diaphragm seal and flange to fixing on tank.
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