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SECTION 1 - INTRODUCTION
1-1. General
The Barton Models 200A and 227A/C measure differential pressure, uid ow
rate, or liquid level. For uid ow measurements, the indicator is connected
by piping to the low- and high-pressure sides of a primary device (e.g., orice
plates, venturis, or ow tubes) located in the process run. For liquid level appli-
cations, variations in the level of the liquid within the process vessel produce
changes in differential pressure used to indicate the liquid height.
The indicating pointer travels through a 270 degree arc over a six-inch diameter
scale. The movement has a micrometer screw for range adjustment. Pointer hub
adjustment can be made without removing the scale plate or pointer. Range and
linearity adjustments are accessible after removal of the scale plate.
1-2. Main Components
The 200A consists of two major components: an actuating unit (DPU) and the
case enclosed indicating instrument.
A. Actuating Unit (DPU) - 200A uses 199 DPU, 227A uses a 224 DPU, and
227C uses a 224C DPU. For detailed information on the actuating DPU,
see the appropriate (separate) DPU manual.
B. Indicator
1-3. Indicator Specications
Accuracy:
0-10" w.c. to 0-349" w.c.
(255 mm to 890 m) ............ ±1/2% of full scale DP
0-350" w.c. to 0-100 psi
(890 m to 6.7 bar) ............... ±3/4% of full scale DP
Temperature Limits ................. -40°F/°C to +180°F (+80°C);
+35°F to +180°F (+1°C to +80°C)
for water lled units
Dimensions............................. per model number and housing rating. See
ODD Drawings in Section 5.
1-4. Theory of Operation
The bellows within the DPU moves in response to changes in the DP monitored
at the high and low pressure sides of the primary device installed in the process
run. The DPU bellows movement is mechanically transferred to the indicator
mechanism through a rotating torque tube shaft. As the torque tube rotates, the
drive arm transmits the motion through the connecting link to the indicating
pointer. The pointer travels through a 270 degree arc to indicate measurement
on the 6-inch scale plate.
The 6-inch scale can be printed as required, in uniform increments for DP, SP,
or liquid height or in square-root increments for direct ow measurements. Spe-
cial scales can be furnished to indicate the amount of liquid in a tank.
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