Ashcroft K8 - Industrial Pressure Transducer - Manual

© 2012 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614, USA. Tel: 203-378-8281 • Fax: 203-378-0499, All specifications are subject to change without notice.
All sales subject to standard terms and conditions. All rights reserved. www.ashcroft.com. I&M011-10063-1/01 (250-2924). Rev. A 7/12
1. GENERAL:
A failure resulting in injury or damage may
be caused by excessive overpressure,
excessive vibration or pressure pulsation,
excessive instrument temperature, corro-
sion of the pressure containing parts, or
other misuse. Consult Ashcroft Inc., Strat-
ford, Connecticut, USA before installing if
there are any questions or concerns.
2. OVERPRESSURE:
Pressure spikes in excess of the rated
overpressure capability of the transducer
may cause irreversible electrical and/or
mechanical damage to the pressure mea-
suring and containing elements.
Fluid hammer and surges can destroy any
pressure transducer and must always be
avoided. A pressure snubber should be
installed to eliminate the damaging ham-
mer effects. Fluid hammer occurs when
a liquid flow is suddenly stopped, as with
quick closing solenoid valves. Surges
occur when flow is suddenly begun, as
when a pump is turned on at full power or
a valve is quickly opened.
Liquid surges are particularly damag-
ing to pressure transducers if the pipe
is originally empty. To avoid damaging
surges, fluid lines should remain full (if
possible), pumps should be brought up to
power slowly, and valves opened slowly.
To avoid damage from both fluid hammer
and surges, a surge chamber should be
installed.
Symptoms of fluid hammer and surge's
damaging effects:
• Pressure transducer exhibits an output
at zero pressure (large zero offset).
• Pressure transducer output remains
constant regardless of pressure
• In severe cases, there will be no output.
FREEZING:
Prohibit freezing of media in pressure
port. Unit should be drained (mount in
vertical position with electrical termination
upward) to prevent possible overpressure
damage from frozen media.
3. STATIC ELECTRICAL CHARGES:
Any electrical device may be susceptible
to damage when exposed to static electri-
cal charges. To avoid damage to the trans-
ducer observe the following:
• Operator/installer should follow proper
ESD (electrostatic discharge) protection
procedures before handling the pressure
transducer.
Note: The shield and drain wire in the
cable (if supplied) is not connected to the
transducer body, and is not a suitable
ground.
MOUNTING
The transducer requires no special mount ing
hardware, and can be mounted in any plane
with negligible position error.
Although the unit can withstand normal
vibration without damage or significant
output effects, it is always good practice to
mount the transducer where there is mini-
mum vibration.
For units with NPT type pressure fittings
apply teflon tape or an equivalent sealant to
the threads before installing.
When tightening, apply a wrench to the hex
wrench flats located just above the pres-
sure fitting.
DO NOT tighten by using a pipe
wrench on the housing.
POWER SUPPLY – K1 Models Only
The supply voltage for the 1-5 and 1-6 Vdc
output transducers must be within the range
of 10 to 36 Vdc. The maximum supply volt-
age for a 4-20mA current output transducer
is 36 Vdc while the minimum supply voltage
is dependent upon the loop resistance of the
circuit. The load limitation chart shows the
minimum supply voltage (V
min
) required for a
given loop resistance (R
LOOP
).
NOISE
For minimum noise susceptibility, avoid
run ning the transducer’s cable in a con duit
that contains high current AC power cables.
Where possible avoid running the cable near
inductive equipment.
SHIELD WIRING
Connect the braided shield to the guard
terminal on the reading instrument (meter,
etc.) if available or to ground or to the power
supply negative terminal.
V
min
= 10V+ (.022A x R
L
)
R
L
= R
S
+ R
W
R
L
= Loop Resistance (ohms)
R
S
= Sense Resistance (ohms)
R
W
= Wire Resistance (ohms)
1000
750
500
250
0
0 36 20 10
1182
30
Load Limitations 4-20mA Output Only
(R
LOOP
)
OPERATING
REGION
WARNING! READ
BEFORE INSTALLATION
m
K1, K2, K8
PRESSURE TRANSDUCER
INSTRUCTION SHEET
ADJUSTMENT POTENTIOMETERS
The zero and span pots are accessible
through the top of the case. Loosen the four
screws and separate the top carefully. The
zero pot is marked with a white dot.
VENT TUBE
The cable will have a clear Teflon vent tube
that's required at pressure below 500 psi to
provide atmospheric reference. The open
end should be placed in a dry area.
OUTPUT – K8 Only
Sensitivity may be from 6 mV/V to 18 mV/V
for any individual transducer. Zero offset is
within ±3 mV/V. Output is proportional to
supply voltage (ratiometric).
EXCITATION – K8 & K2
For proper operation a voltage within the
range of 5 to 10 Vdc must be applied be-
tween the transducer’s supply terminals. m