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3. Operating principle
.
The output of the pressure sensor is a voltage in proportion with the input pressure. This voltage
gets amplified by a high-impedance symmetrical amplifier. The amplified signal goes to a
voltage-current transformer. This is the place where the 4 mA output current is set as „zero"
pressure, and the 20 mA output current is set as the effect of the pressure that corresponds with
the end-position of the scale. A voltage of 12-28 VDC is necessary for the operation of the
device; the system generates the 4-20 mA current in accordance with the measured pressure in
the above supply-voltage circuitry (2-wire).
4. Mechanical design of the device; installation
.
4.1. Mechanical design of the device
The members of the DT7200 family may be divided into two types in terms of temperature
ranges:
— normal temperature, DT7200 L (Figure 1), and
— high temperature, DT7200 M and DT7200 H (Figure 2).
The operating temperature ranges belonging to the various types are presented in Chapter 8.
Technical Specifications.
In the case of connection types G ½"A and M20x1,5 the seal must be applied in accordance
with the way shown in Figure 3. It is the User's responsibility to ensure that appropriate,
chemical- and heat-resistant seals are used.
In the case of the connection type G ¾"A with front membrane (see Figure 4) the sealing
function is performed by the "O"-ring of the plane above the thread. Its material has been
selected in accordance with the medium to be measured.
Figure 1. DT7200 L
Figure 2. DT7200 M or DT7200 H
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