- ページ 5

計測機器 Ashcroft a4aのPDF インストレーション＆メンテナンス・マニュアルをオンラインで閲覧またはダウンロードできます。Ashcroft a4a 20 ページ。 Precision pressure gauge

ページを印刷する

BEZEL

EXTERNAL "ZERO"

ADJUSTMENT

Compound Gauge

Measures and indicates pressure

above and below ambient pres-

sure, using ambient pressure as a

reference point. A compound

gauge is a combination of a

gauge pressure and a vacuum

pressure gauge.

Absolute Pressure Gauge

Measures and indicates pressure

above zero absolute pressure,

using absolute zero pressure as a

reference point. All measure-

ments made with an absolute

pressure gauge will be positive as

it is impossible to generate a

pressure below that of zero

absolute pressure.

NOTES:

1. Ambient pressure equals pressure surrounding the mea-

suring element, generally atmospheric pressure.

2. The Ashcroft A4A absolute pressure gauge does not

incorporate automatic barometric pressure compensation.

The barometric pressure at the time of use must be set by

using the External Dial Adjuster.

Optional Features

Where specified, gauges have been equipped with auto-

matic thermal compensator, slotted link for protection

against sudden pressure release, peak load indicating

pointers or other optional features. See Section 2.3.5 for

Complete Details on Available Options.

2.3

CONSTRUCTION

2.3.1

CASE AND BEZEL

Solid Front Case

A solid front case of cast aluminum protects the operator

POINTER

WINDOW

GASKET

DIAL

CASE

when working with high pressure systems. In the event of

tube rupture through excessive over pressure, protection is

provided by this wall as pressure release will be directed out

the back of the gauge, away from the operator

Blow-Out Safety Back

A light gauge stainless steel disc, covering the entire back

of the gauge case, is spring-loaded against a seal

machined in the periphery of the case. An abnormal rise of

pressure within the gauge case causes this disc to flex out-

ward, releasing the pressure.

Bezel

A hinged bezel protecting the dial and pointer is equipped

with an external dial zero adjustment. It is also the mounting

for the lens.

External dial Zero Adjustment

A zero adjustment knob on the front of the gauge case

makes it possible to set dial zero to atmospheric pressure

or other benchmarks required.

Limit Stops

High and low pressure limit stops are mounted on the interi-

or of the gauge case, restraining tube tip travel within the

rated operating range of the gauge. The limit stops protect

the movement from becoming disengaged due to excessive

tip travel. They do not protect the Bourdon tube from dam-

age to over-pressure.

2.3.2

BOURDON TUBE SYSTEM

The Ashcroft A4A Bourdon tube is a product of more than

40 years of intensive, continuous research. The "unitized"

one-piece tube system is an outstanding example of mod-

ern technology.

Through exclusive Ashcroft A4A Bourdon tube designs and

manufacturing techniques, uniform stress distribution is pro-

vided in a wide range of tubes of varying cross sectional

configurations. All A4A tubes are formed from a single piece

of seamless tube material.

Tubes of 403 stainless steel are standard for ranges of 50

psi and above. Beryllium Copper may be supplied for low

PRESSURE

RELIEF

DISC

MOVEMENT

BOURDON

TUBE

PRESSURE

ELEMENT