Ashcroft 2279 - Duratran® Pressure Transmitter - Manual

Installation and Maintenance Instructions for
ASHCROFT ® Type 2279
Duratran ® Pressure Transmitter
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 mecha-
nism and pointer in traditional pressure gauge fashion. The indi-
cating portion is therefore calibrated and maintained in accor-
dance 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 condi-
tioned 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 non-
contacting 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.
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 rota-
tion 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 resis-
tance 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 (+).
Figure 1 – Figure 2 –
X = TRANSMITTER
PS = POWER SUPPLY (16-40V max)
R = 250
Ω RESISTOR
A = AMMETER (to 20mA)
V
= VOLTMETER (to 5V)
© 2007 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: 203-378-8281, Fax: 203-385-0499, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M00810043-9/01 (Form No. 250-2598) Rev. 10/12
A
PS
4-20mA
RED
R (250) Ω
BLACK + –
+ –
+
X
V
PS
1-5V
RED
BLACK
+
X
SUPPLY VOLTAGE
L
O
A
D
R
E
S
IS
T
A
N
C
E
O
H
M
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1400
1000
500
0
0 12 24 36 40