Principle Of Operation And Construction - ABB 265DS Operating Instruction

Design and function
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3.1

Principle of operation and construction

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The transmitter has a modular structure and consists of measuring equipment with integrated
adjustment electronics, as well as electronics with a control unit.
265Dx
The fully welded measuring cell is a two-chamber system with an interior overload diaphragm,
interior silicon differential pressure sensor, and silicon absolute pressure sensor. The absolute
pressure sensor, which is only pressurized from the positive side (⊕), is used as a command
variable for compensating static pressure. A capillary tube is used to connect the differential
pressure sensor and the negative side of the measuring cell. The existing differential pressure
(dp) and static pressure are transferred to the measuring diaphragm of the silicon differential
pressure sensor and of the absolute pressure sensor via the isolating diaphragms and filling
liquid.
265Vx
The fully welded measuring cell is a two-chamber system with an interior overload diaphragm
and interior silicon absolute pressure sensor. The existing absolute pressure (pabs) is
transferred to the measuring diaphragm of the silicon absolute pressure sensor via the isolating
diaphragm and filling liquid.
Even a very slight deflection of the silicon diaphragm will change the output voltage of the pick-
up system. This output voltage, which is proportionate to the pressure, is transformed into an
electrical signal by the matching electronics and main electronics.
Depending on its design, the transmitter is connected to the process by means of an oval flange
with a fastening screw thread (7/16-20 UNF or to DIN 19213 (M10/M12)), a 1/4-18 NPT female
thread, or a remote seal.
The transmitter operates on the basis of two-wire technology. The same wires are used for the
operating voltage (device-specific) and the output signal (4 ... 20 mA or digital). The electrical
connection is established via a cable entry or plug.
22 265Dx, 265VS IM/265D/V-EN-02