KPSI™ Level & Pressure Transducers: Options

Expedite Shipment Service

Standard lead times for many of Pressure SystemsÕ line of KPSI Level and Pressure Transducers are 5 working days. At a premium, PSI offers an Expedite Shipment Service in order to ship transducers within 1-4 working days. This service includes requirements for custom pressure ranges within the limits of the relevant transducer models as well as custom cable lengths. Expedite shipment service is available on most models. Consult our Customer Service staff for availability.

Reference Pressure Formats

KPSI Transducers are available in three different Reference Pressure Formats to meet varying requirements. The format indicates whether the sensor is referenced to atmospheric pressure (vented gage), a hard vacuum (absolute), or a simulated atmospheric pressure (sealed gage).

Vented gage reference is usually used in lower full-scale range transducers where the sensor must track changes in atmosphere to maintain stated accuracy. Care must be taken to employ appropriate moisture protection to prevent humidity from entering the transducer via the vent tube.

Sealed gage and absolute reference is typically used when the full-scale range is above 700 ft (210 m) H₂O. Changes in atmospheric pressure have negligible impact on the accuracy of transducers at that range and moisture protection is not a concern since no vent tube is required. Sealed gage units are absolute units that are electrically adjusted to simulate reference to the atmospheric pressure at site of the installation. Base elevation with respect to sea level of the site must therefore be specified when ordering sealed gage transducers. Consult our Technical Support staff if you need assistance in choosing the reference pressure format.

Transducer Output

A variety of electrical Transducer Output signals are available to facilitate interfacing to almost any system. The most popular output signal is 4-20 mA, which is transmitted over two wires along with power for the transducer. Transducers with this output are typically referred to as transmitters and interface with almost any data logger or PLC.

Amplified voltage output is also commonplace requiring three wires for power and output signal. Most common is 0-5 VDC but other voltage ranges include 1-5, 0-7.5, 0-10, and others. The full-scale voltage output can be factory-adjusted to as much as 2.5 VDC less than the anticipated excitation voltage supply. Specify the voltage range required when ordering VDC output transducers.

Data loggers sometimes require an unamplified millivolt level output signal from the transducer. This output can take two forms depending on the available excitation voltage and system capabilities. Ratiometric mV output is required when the excitation is externally regulated or the system interfaced with the transducer is capable of compensating for fluctuations from the excitation supply. Such fluctuations to the supply will cause the output signal to fluctuate, and must therefore be measured and compensated. The benefit of ratiometric design is that the output signal can also be compensated for temperature changes to the pressure sensor if the voltage sense lines are employed. The non-ratiometric mV output version is used when the excitation voltage cannot be externally regulated or the system is incapable of compensating for changes to the excitation voltage.

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Electrical Connection

Two basic transducer Electrical Connection options are offered to facilitate submerged use in different environments.

The most common connection is the submersible cable exit where a simple cap is installed to seal the cable exiting the rear of the transducer and the cable is left exposed to the liquid media.

For more rugged and durable connections, a 1/2"-14 male NPT fitting is installed to enable the transducer to be attached to a comparable conduit. Both electrical connections utilize a gland seal to prevent ingress of the liquid media into the transducer.

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Temperature Sense Output

As an option, a precision silicon temperature sensor can be installed within the transducer to provide a separate 4-20 mA temperature measurement output over the range of 0 to 50¼C or -20 to 60¼C. The accuracy of the temperature measurement is ±4¼C.

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Transducer Housing Assemblies
The transducer assemblies are most commonly made from 316 stainless steel, which offers good compatibility for most water and hydrocarbon liquid applications. Alternatively, the transducer assembly can be made from titanium, which offers superior compatibility to salt water and chemical liquid applications.

Cable Seals
The molded cable seal is KPSIÕs standard offering and provides a very reliable injection molded polyurethane seal. The gland cable seal is primarily used for teflon cable and incorporates a compressed Viton¨ gland.

Transducer Cable
The jacket on our transducer cable is typically constructed from polyurethane, which provides excellent general-purpose use and reliability with good flexibility and economy. For liquid media such as hydrocarbons and other chemicals, Tefzel¨ can be specified providing excellent compatibility and maintaining all the features of the polyurethane though somewhat less flexible and more expensive.

Consult our Technical Support staff for the material best suited for the anticipated media.

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