Reference Manual
00809-0100-4302, Rev BA
January 2008
4-3
Rosemount 1153 Series B
Figure 4-2. Electrical Block
Diagram.
THE
δ
-CELL
™
SENSOR
Process pressure is transmitted through an isolating diaphragm and silicone
oil fill fluid to a sensing diaphragm in the center of the
δ
-
Cell
. The reference
pressure is transmitted in like manner to the other side of the sensing
diaphragm.
The position of the sensing diaphragm is detected by the capacitance plates
on both sides of the sensing diaphragm. The capacitance between the
sensing diaphragm and either capacitor plate is approximately 150 pf. The
sensor is driven through transformer windings by an oscillator at roughly 32
kHz and 30 V
p-p
.
DEMODULATOR
The demodulator consists of a diode bridge that rectifies the ac signal from
the sensor cell to a dc signal.
The oscillator driving current, I
ref
(the sum of the dc currents through two
transformer windings) is controlled to be a constant by an integrated circuit
amplifier.
The dc current through a third transformer winding is a current directly
proportional to pressure, i.e.,
The diode bridge and span temperature compensating thermistor are located
inside the sensor module. The effect of the thermistor is controlled by
resistors located in the electronics housing.
LINEARITY
ADJUSTMENT
Linearity is adjusted by a variable-resistance network, capacitor, and diodes.
The currents generated through this part of the circuit are summed into the
inputs of the oscillator control circuit. This provides a programmed correction
that raises the oscillator peak-to-peak voltage to compensate for first-order
nonlinearity of capacitance as a function of pressure.
OSCILLATOR
The oscillator has a frequency determined by the capacitance of the sensing
element and the inductance of the transformer windings.
The sensing element capacitance is variable. Therefore, the frequency is
variable about a nominal value of 32 kHz.
Demodulator
Current
Detector
Oscillator
Osc.
Control
Amp.
Curr.
Control
Amp.
Voltage
Regulator
Test
Signal
Current
Limiter
Current
Control
+
–
Reverse
Polarity
Protection
Sensor
I
diff
fV
p
p
–
C
2
C
1
–
(
)
=
Summary of Contents for Rosemount 1153 Series B
Page 6: ...Reference Manual 00809 0100 4302 Rev BA January 2008 Rosemount 1153 Series B iv ...
Page 9: ...Reference Manual 00809 0100 4302 Rev BA January 2008 TOC 3 Rosemount 1153 Series B ...
Page 10: ...Reference Manual 00809 0100 4302 Rev BA January 2008 Rosemount 1153 Series B TOC 4 ...
Page 12: ...Reference Manual 00809 0100 4302 Rev BA January 2008 Rosemount 1153 Series B 1 2 ...
Page 50: ...Reference Manual 00809 0100 4302 Rev BA January 2008 Rosemount 1153 Series B 5 12 ...
Page 62: ...Reference Manual 00809 0100 4302 Rev BA January 2008 Rosemount 1153 Series B Index 2 ...
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