Ashcroft 2279 User Manual

Installation and Maintenance Instructions for

A

PS

4-20mA

RED

R (250) Ω

BLACK

+ –

+ –

+

X

V

PS

1-5V

RED

BLACK

+

X

SUPPLY VOLTAGE

LOAD RESISTANCE OHMS

1400

1

000

5

00

0

0 12 24 36 40

ASHCROFT®Type 2279
Duratran®Pressure Transmitter

igure 1 –

F

X = TRANSMITTER
PS = POWER SUPPLY (16-40V max)
R=250 Ω RESISTOR
A=AMMETER (to 20mA)
V=VOLTMETER (to 5V)

Figure 2 –

OPERATING PRINCIPLE

This instrument is based on pressure measuring systems that
have made Ashcroft Duragauge

®

gauges the standard of perfor-

mance throughout the world.

The Bourdon tube in this instrument drives the geared mecha­nism and pointer in traditional pressure gauge fashion. The indi­cating portion is therefore calibrated and maintained in accor­dance with good pressure measurement practice.

The same Bourdon tube also positions a unique self-regulating
photo-optic position sensing system to produce a dc electronic
signal proportional to the pressure value. This signal is condi­tioned to a standard 4-20mA dc output over two wires, powered
by a dc supply between 12 and 40 volts. Since there is no
mechanical sliding or other frictional interaction within the non­contacting photo-optic system, the transmitting function is highly
reliable and not subject to wear.

INSTALLATION PRECAUTIONS

To get the maximum value and performance there are a few
good installation practices to follow:

1) Pulsation, Vibration and Shock – The excellent sensitivity

of the photo-optic system will reliably sense and transmit any
motions of the Bourdon tube, whether caused by pressure
changes or installation seismic effects. Therefore, please
mount the instrument on a stable surface or piping system
free from vibrations and mechanical shock and – if pressure
pulsations are present that you don’t want to transmit –
use a suitable snubber or throttling valve to exclude these
effects. Metal tubing is recommended to pipe pressure to
the instrument. The Ashcroft 1115A armoured capillary line
with fittings is available to remote mount the Duratran.

© 2007 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: [phone], Fax: [phone], www.ashcroft.com
All sales subject to standard terms and conditions of sale.

I&M00810043-9/01 (Form No. 250-2598) Rev. 10/12

2) Process Fluid Effects – Make sure the process fluid will not

corrode or overheat the wetted materials of the pressure
measuring systems. These materials are clearly marked on
the dial face. Ashcroft chemical seals are readily available for
corrosive fluids.

3) Ambient Temperature – Most accurate results will be

obtained if the instrument is mounted indoors, although it is
well protected with hermetic sealing to operate outdoors over
a range of –40° to 160°F with some accompanying error (see
specifications).

4) Electrical fitting – Avoid disturbing the hermetic seal on the

electrical connection by holding the wrench flats against rota­tion when installing electrical fittings.

5) Pressure Fitting – Always use the wrench flats provided
when connecting piping to the transmitter – DO NOT USE

THE HOUSING AS A HANDLE.

OUTPUT CONNECTIONS – See Figure 1.

Voltage – Internal regulation permits accurate transmission

within widely varying applied dc charge – consult the load resis­tance vs voltage curve in Figure 1.

Load Resistance – Maximum allowable load resistance for a
given supply voltage can also be determined from Figure 2.

Polarity – Although the transmitter is protected against reverse
polarity, there will be no usable signal unless proper dc polarity
is observed. NOTE THAT THE RED LEAD IS POSITIVE (+).

Installation and Maintenance Instructions for
ASHCROFT®Type 2279
Duratran®Pressure Transmitter

CALIBRATION

If it is necessary to rezero the instrument, (i.e. to correct for
head effect in the piping), this may be done by removing the
front ring and window. The indicating pointer is set by the
micrometer adjustable hub. Zero and span adjustments are
accessible from the front through holes in the dial; use a small
screwdriver for this. The case should only be opened in a dry
and clean environment, preferably in an instrument shop.

Complete recalibration may be required after extended service

or if the instrument has been overpressured.

Calibration should be checked against a test gauge and pres­sure source, or a deadweight tester, appropriate to the range of
the transmitter. ANSI B40.1, “Gauges – Pressure Indicating Dial
Type – Elastic Element,” recommends that the pressure stan­dard be at least four times as accurate as the instrument being
tested. A power supply and milliameter, or voltmeter and resis­tor, of suitable accuracy are also required to test the transmitter
output. These are to be connected in series with the output
leads, observing correct polarity, as in Figure 1.

With the input pressure at zero, the micrometer pointer adjust­ment and the “zero” potentiometer should be adjusted for zero
indication and 4mA output respectively. The pressure should
then be raised to full scale and, if the output is not 20mA, the
“span” potentiometer used to correct the span error. The zero
should then be rechecked. If an indication span error is found, it
is necessary to open the back of the case and adjust the slide.
More information on indicator calibration is available in Ashcroft
Maintenance and Repair Manual. visit www.ashcroft.com for the
most up to date version. When the indication span and zero are
correct, replace the back of the case prior to final calibration of
the transmitter. Caution: do not adjust the “zero” and “span”

potentiometers while the back of the case is open; ambient
light may cause erratic results. Mechanical zero/span adjust-

ment should normally not require any electrical adjustment.

The front window and rear cover must be firmly and evenly
tightened to prevent moisture or corrosives from damaging
the circuit board.

© 2007 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: [phone], Fax: [phone], www.ashcroft.com
All sales subject to standard terms and conditions of sale.

I&M00810043-9/01 (Form No. 250-2598) Rev. 10/12