Emerson 1154 manual Overview Transmitter Operation, Section, Rosemount, Reference Manual

Reference Manual

00809-0100-4514, Rev BA January 2008

Rosemount 1154

Section 4 Operation

OVERVIEW

TRANSMITTER OPERATION

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1 Transmitter Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1The δ-Cell Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-3 Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-3 Linearity Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-3 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-4 Voltage Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-4 Zero and Span Adjustments . . . . . . . . . . . . . . . . . . . . . . . page 4-4 Current Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-4 Current Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-4 Reverse Polarity Protection . . . . . . . . . . . . . . . . . . . . . . . . page 4-4

This section provides brief descriptions of basic transmitter operations in the following order:

•Transmitter Operation

•The ￿-Cell™Sensor

•Demodulator

•Linearity Adjustment

•Oscillator

•Voltage Regulator

•Zero and Span Adjustments

•Current Control

•Current Limit

•Reverse Polarity Protection

The block diagram in Figure 4-2 on page 4-3illustrates the operation of the transmitter.

The Rosemount 1154 Alphaline Pressure Transmitters have a variable capacitance sensing element, the δ-Cell (Figure 4-1 on page 4-2). Differential capacitance between the sensing diaphragm and the capacitor plates is converted electronically to a 2-wire 4–20 mA dc signal.

P = K		⎛ C2	– C1⎞
	1	⎜ --------------------	⎟
		⎝ C1	+ C2⎠

Where:

Pis the process pressure.

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