Emerson Rosemount 1152 Alphaline, Reference Manual

Page: 35 / 68

Reference Manual
00809-0100-4235, Rev BA
April 2007
Rosemount 1152
www.emersonprocess.com/rosemount/nuclear
Section 4 Operation
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1
Transmitter Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1
Demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-4
Voltage Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-5
Zero and Span Adjustments . . . . . . . . . . . . . . . . . . . . . . . page 4-5
Current Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-5
Current Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-5
Reverse Polarity Protection . . . . . . . . . . . . . . . . . . . . . . . . page 4-5
OVERVIEW
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
TRANSMITTER
OPERATION
.
The block diagram in Figure 4-1 on page 4-3 illustrates the operation of the
transmitter.
Rosemount 1152 Alphaline Pressure Transmitters have a variable
capacitance sensing element, the
␦
-Cell (see Figure 4-2 on page 4-4).
Differential capacitance between the sensing diaphragm and the capacitor
plates is converted electronically to a 2-wire, 4–20 or 10–50 mA dc signal.
Where:
P is the process pressure.
K
1
is a constant.
P K
1
C
2
C
1
–
C
1
C
2
+
--------------------
⎝ ⎠
⎜ ⎟
⎛ ⎞
=