Delta Controls DPR-2000 - Manual (Page 17)

A 15 IOM-DPCDPR-A: FEB 2014
6. CONSTRUCTION
6.1. Measurement Principles, Electronic System.
DPC... electronic pressure transmitters and DPR... electronic differential pressure transmitters work by
converting changes in the resistance of a piezoresistance bridge, which are proportional to the measured
pressure, into a standard current signal. The active sensing element is a silicon diaphragm with piezoresistors,
separated from the medium by a sealing diaphragm and manometric fluid. The electronic system digitally
processes the measurement signal and generates output signals: an analogue 4÷20 mA signal with a digital
communication signal.
A block diagram of the transmitter is presented in Figure 1. At the circuit input two analogue signals are provide:
the measured pressure reflecting and the sensing module temperature. These signals are digitalized and
provide to a microprocessor input which controls the transmitter’s operation. Using input data during the
production process adjusts for thermal errors and carries out linearization. After digital processing, the signal is
converted into an analogue 4÷20mA current signal again, with a superimposed digital communication signal.
For communication with the transmitter via the signal line a special Delta Controls KAP communicator, or a
computer meeting the requirements given in 10.2.4, are used.
The transmitter’s output is fitted with a radio-noise filter and other elements protecting against ESD.
6.2. Construction.
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.
DPC..., DPR... transmitters are equipped in LCD display with LED back lighting, enabling reading two the
process variables simultaneously as well as the unit process variable reading. The electronic board is closed in
poly-carbonate casing. The casing construction enables turning of display by
 
On the electronic casing the set of buttons is placed, used to local adjustment.
The transmitters construction enables connecting of the separately compensated measuring sensor to
separately compensated electronic board enables fast servicing at the plant.
The electronic circuit of sensor has a galvanic separation from measuring line. Thanks of that construction the
measurement susceptibility at interferences is reduced as well as the enlarged safety of work in the Ex and
flameproof applications.
In dependence from needs we can choose a needed bank of coefficients memory for transmitter work. DPC...,
DPR...transmitters monitor work of their equipment as well as the calculation correctness and in case of rises
of incorrigibility inform about mistakes displaying the announcement on LCD screen as well as putting out the
alarm current in current loop.
6.2.1. The pressure connectors may be fitted to the DPC... sensing module as in figures 5a, 6a, 7a, 8 and other.
The
DPR… transmitters have the sensing modules with two P-type connectors, or C-type connecting covers for
installation on a valve manifold (figure 9). The sensing modules, for both types, are equipped with a diaphragm
separating the internal part of the head from the measuring medium.
6.2.2. For measuring the pressure of dense, chemically reactive or hot media, the transmitter may be
additionally fitted with various types of diaphragm seal depending on the type of medium and the
conditions in which measurement is carried out (see catalogue car
ds “Diaphragm Seals).
The diaphragm seal transmits the pressure obtained from the medium. The pressure is transmitted via a
manometric fluid which fills the space between the diaphragm of the seal and the diaphragm of the
sensing module. In the case of remote diaphragm seals, pressure is transmitted via a capillary linking
the transmitter’s sensing module to the diaphragm seal. The seals construction depends on the
medium properties and operating conditions for which they are intended.
Technical data rela ting to the diaphragm seals’ dimensions and operating conditions can be found in catalogue
cards “DIAPHRAGM SEALS”.
6.2.3. The DPR
… transmitters may be fitted with an single direct diaphragm seal, mounted on the “+” pressure
input of the sensing module, wh ile the “–” input is a ¼NPT F connector (fig.10).
The DPR-2200ALW transmitter is fitted with two diaphragm seals and can be produced in two versions:
-
with one direct diaphragm seal and one remote diaphragm seal (fig.15);
- with two remote diaphragm seals (fig.14).
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