A1 25 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 BELL202 and HART rev5
communication stack enables communication with the transmitter via a modem 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 side covers, 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 and is possibility a change of display position turning it with 90° angle to required position (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 membrane 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 membrane which separates the sensor from the medium (APR… transmitters have a two
separated membranes). Measuring heads are equipped with process connectors as at fig. 5a, 6a, 7a or other.
APR… transmitters measured head has two process connectors type P or C connector (fig. 9) for assembly on
manifold. Measuring head of APR-2000GALW is intended to low pressures of gases with overpressure to 100
(or 35) kPa. 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 17.
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.
To Next Page
Loading...
