Description And Specifications; Features And Applications; Operation; Sensor Specifications - Emerson ROSEMOUNT 320HP Instruction Manual

MODEL 320HP
GENERAL DESCRIPTION AND SPECIFICATIONS
• CORROSION-RESISTANT, WEATHERPROOF CONSTRUCTION permits installation in
almost any environment.
• UNIQUE SENSOR DESIGN provides accurate, stable pH measurement in high purity water.
• ELECTRONICALLY SHIELDED GLASS ELECTRODE protects against electrostatic
noise pickup.
• INCLUDES ROTAMETER AND NEEDLE VALVE to assure an accurate, stable measure-
ment.
• CONVENIENT SHELF to hold electrodes for buffer calibration.

1.1 FEATURES AND APPLICATIONS

The Rosemount Analytical Model 320HP High-Purity
pH Sensor is uniquely designed for pH measurement
in aqueous solutions of very low dissolved solids con-
tent (below 50 microsiemenss). The sensor assembly
consists of a stainless steel flow cell, glass electrode,
a double junction Kynar
designed liquid junction, temperature compensator,
rotameter, needle valve and a weatherproof junction
box containing an optional preamplifier. All compo-
nents are mounted on an ABS plate which may be
attached to a wall or clamped (optional) to a two-inch
pipe.
The electrical resistance of high-purity water is very
high, typically one megohm or more. Such liquids can
generate a considerable static charge when flowing
over an essentially nonconductive (plastic) surface.
An adequate discharge path to a good earth ground
must be provided for this static charge; otherwise, it
can be easily picked up by the high impedance pH
electrode causing excessive noise in the measuring
signal. The well-grounded metallic flow cell in the
Model 320HP High-Purity pH Sensor surrounds the
pH electrode and provides an effective discharge path
to ground for any static charges. It also serves as an
electronic shield against outside interference from AC
power lines, arcing electrical equipment, and other
similar sources of noise.
SECTION 1.0
1 reference cell with specially

DESCRIPTION AND SPECIFICATIONS

1.2 OPERATION

Accurate pH measurement in high-purity water
depends on a stable reference junction potential, and
this requirement is met by the unique design of the ref-
erence junction in the high-purity sensor. The con-
struction of the junction serves to minimize any
changes in junction potential which are caused by vari-
ations in flow rate of the high-purity water over the
junction surface. The flowmeter and needle valve aid in
maintaining the low, constant sample flow required for
a stable reference junction potential.

1.3 SENSOR SPECIFICATIONS

Style: Flow-through
Wetted Materials: Kynar, Buna-N, glass, stainless
steel, ABS, Teflon 2
Range: 0 to 14 pH
Sample Temperature: 4°C to 71°C (39°F to 160°F)
Sample Pressure Required: 5 to 10 psig
Sample Flow Rate: Constant in the region of 0.8 to
2.4 gal/hour
Process Connections: 1/4-inch tube
Reference Electrode: Sealed, double junction
Measuring Electrode: Glass, GPHT (0-13pH)
1
Kynar is a registered trademark of Elf Atochem North America, Inc.
2
Teflon and Viton are registered trademarks of E.I. duPont de Nemours & Comp.
SECTION 1.0
Viton 2 , Polypropylene
1