Ashcroft k8 지침서

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K1, K2, K8

PRESSURE TRANSDUCER

INSTRUCTION SHEET

WARNING! READ

BEFORE INSTALLATION

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 mounting

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

given loop resistance (R

NOISE

For minimum noise susceptibility, avoid

running the transducer's cable in a conduit

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.

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.

Load Limitations 4-20mA Output Only

1182

1000

) required for a

min

LOOP

)

LOOP

750

500

250

OPERATING

REGION

= 10V+ (.022A x R

)

min

= R

+ R

= Loop Resistance (ohms)

= Sense Resistance (ohms)

= Wire Resistance (ohms)