Keller sensors explained for pressure, level, and OEM measurement

What Keller sensors are used for

Keller sensors are typically specified as precision pressure measurement components and instruments, not as general-purpose electronic modules. The Keller Pressure product family is built around piezoresistive pressure sensing, with products ranging from bare OEM pressure transducers to industrial pressure transmitters, submersible level probes, digital pressure gauges, and data loggers. For engineers comparing sensors and modules, the real question is not only whether a Keller sensor can measure pressure. It is which mechanical configuration, pressure reference, electrical output, media compatibility, and accuracy class fit the application.

According to Keller Pressure’s official company information, the business was founded in 1974 in Winterthur, Switzerland, and its product positioning remains closely tied to piezoresistive pressure measurement. The company’s public technical material also states that its production covers more than one million measuring cells annually, with significant manufacturing and calibration activity located at its Winterthur site. For buyers, these details are relevant because pressure sensors are rarely interchangeable by part number alone. Measurement reliability depends on the package, calibration, media isolation, and the full installation environment.

How Keller pressure measurement technology works

Most Keller sensors used in industrial and OEM applications are based on piezoresistive technology. In simple terms, pressure causes mechanical deformation in a sensing element, and that deformation changes electrical resistance. The electronics then convert the change into a usable signal such as millivolts, volts, 4–20 mA, I2C, RS485, CANopen, or IO-Link, depending on the product series and configuration.

The practical advantage of piezoresistive pressure sensing is that it can support compact construction, good sensitivity, and a wide range of pressure ranges. The sensor element, however, is only one part of the finished product. Keller’s official materials emphasize media-isolated designs, where the pressure medium is separated from the silicon measuring cell by mechanical construction and fill fluid. This matters in applications involving water, oils, fuels, gases, hydraulic fluids, wastewater, or other media that should not directly contact the silicon element.

When comparing Keller sensors with other pressure sensor modules, engineers should separate three layers of performance:

• The sensing element, which determines the basic pressure response and physical measurement principle.
• The mechanical package, including the diaphragm, process connection, housing material, seals, and pressure port geometry.
• The electronics and calibration, which affect output type, temperature compensation, total error band, long-term drift, digital diagnostics, and integration effort.

This layered view helps avoid a common selection error: choosing a sensor by pressure range and output signal while overlooking media compatibility, mounting stress, temperature effects, cable venting, or required approvals.

Main types of Keller sensors

Keller’s public product information groups its pressure measurement products into several practical categories. Exact series names can vary by region and catalogue, so the clearest way to compare the range is by application role.

OEM pressure transducers

OEM Keller sensors are designed for integration into another manufacturer’s equipment. Depending on the series, they may provide an uncompensated output or a conditioned signal. Typical use cases include hydraulic devices, medical or laboratory instruments, gas metering, downhole tools, pumps, compressors, and compact industrial equipment.

For OEM design teams, the main trade-off is integration flexibility versus engineering responsibility. A basic pressure element can be compact and cost-effective at scale, but the equipment manufacturer may need to handle amplification, temperature compensation, mechanical sealing, EMC design, and production calibration. A conditioned OEM transmitter reduces that workload by supplying a more directly usable output, but it may cost more and require more space.

Industrial pressure transmitters

Industrial pressure transmitters combine the sensing element, process connection, housing, and signal conditioning in a field-ready device. They are used in machinery, hydraulic systems, process monitoring, test benches, energy systems, water systems, and general automation. Depending on the model, outputs may include analog current, analog voltage, digital communication, or hybrid arrangements.

For plant and machine builders, transmitters are usually easier to specify than bare OEM elements because they are closer to finished instrumentation. Selection then focuses on pressure range, overload capability, process connection, output type, environmental rating, temperature range, electrical connector, and certification needs.

Level probes and hydrostatic sensors

Submersible level probes measure liquid level by converting hydrostatic pressure into a level value. In water and wastewater applications, the sensor is lowered into a tank, well, river, reservoir, or borehole. The measured pressure corresponds to the height of liquid above the sensing point, after liquid density and the atmospheric pressure reference are taken into account.

Keller’s level probe information highlights piezoresistive level measurement and options for water-related applications. In practice, correct installation is as important as the sensor itself. Cable venting, condensation protection, lightning risk, sludge accumulation, chemical exposure, and mechanical strain relief can all affect long-term reliability.

Digital gauges, loggers, and connected instruments

Beyond analog transmitters, Keller also offers instruments that display, store, or transmit pressure data. Digital gauges are useful for local testing, service work, and calibration checks. Data loggers support unattended monitoring where a continuous PLC connection is unnecessary or impractical. Digitally connected pressure sensors can simplify integration when the host system needs diagnostics, serial identification, or parameter access.

These devices are often selected for workflow as well as accuracy. A maintenance technician may value a rugged display and simple data export, while an automation engineer may prioritize fieldbus compatibility, repeatable configuration, and clean integration into the existing control architecture.

Choosing between gauge, absolute, sealed gauge, and differential measurement

One of the most important specification choices is the pressure reference. Keller’s product material commonly distinguishes gauge, absolute, sealed gauge, and differential pressure configurations. Choosing the wrong reference type can produce an installation that works electrically but reports the wrong value for the process.

Reference type	What it measures against	Typical use	Selection note
Gauge pressure	Local atmospheric pressure	Hydraulics, pneumatics, pumps, tanks, general industrial pressure	Useful when the process result should follow atmospheric changes.
Absolute pressure	A vacuum reference	Barometric measurement, vacuum systems, gas laws, altitude-related calculations	Needed when the measurement must not shift with atmospheric pressure.
Sealed gauge pressure	A sealed internal reference, usually near atmospheric pressure at manufacture	High-pressure systems where venting is impractical	Can be suitable at higher pressures, but it is not the same as true vented gauge measurement.
Differential pressure	Pressure difference between two ports	Filters, flow elements, leak testing, level in pressurized tanks	Line pressure, overload, and media compatibility on both ports must be checked.

For many machinery applications, gauge pressure is the default choice. For atmospheric science, vacuum work, and certain gas calculations, absolute pressure is usually correct. For filter monitoring or flow measurement across an orifice, differential pressure is more appropriate. In pressurized vessels, the distinction between hydrostatic level, head pressure, and gas blanket pressure must be handled carefully.

Specifications that matter before ordering Keller sensors

A pressure sensor specification should be read as a system-level document. The following criteria are often more useful than comparing headline accuracy numbers in isolation.

Pressure range and overload rating

The nominal pressure range should cover normal operating pressure without forcing the sensor to run constantly near full scale. At the same time, oversizing the range can reduce usable resolution. Overload rating matters in pumps, hydraulics, compressors, and test rigs, where pressure spikes may be much higher than steady-state pressure. See also: device architecture.

Accuracy, total error band, and temperature behavior

Accuracy figures are not always directly comparable across manufacturers. Some specifications describe room-temperature accuracy, while others include temperature effects over a defined range. For a serious comparison, check whether the datasheet states non-linearity, hysteresis, repeatability, thermal zero shift, thermal span shift, long-term stability, or total error band.

In outdoor level measurement, mobile hydraulics, aerospace-related testing, or energy equipment, temperature effects can dominate the error budget. A sensor that looks accurate at 20 °C may behave differently in winter, summer, engine-bay, or downhole conditions.

Output signal and integration architecture

Analog 4–20 mA remains common in industrial process environments because it is robust over longer cable runs and easy to diagnose. Voltage outputs are common in embedded systems and test equipment. Digital outputs such as I2C, RS485, CANopen, or IO-Link can reduce analog conversion work and support richer device information, but they also require compatible host electronics and software.

For OEM products, early electrical architecture decisions are important. Changing from an analog pressure element to a digital transmitter late in development can affect PCB layout, firmware, power budget, cable design, EMC testing, and enclosure geometry.

Media compatibility and wetted materials

The process medium determines the required wetted materials, seals, diaphragm design, and filling fluid. Clean dry air, potable water, hydraulic oil, seawater, refrigerant, fuel, hydrogen-containing gases, and aggressive chemicals are not equivalent measurement environments. If the medium is corrosive, viscous, crystallizing, abrasive, hygienic, or ultra-high purity, a standard sensor package may not be suitable.

For this reason, Keller sensor selection should always include a check of wetted parts, sealing materials, pressure port design, and cleaning requirements. In regulated applications such as drinking water, hazardous areas, or medical equipment, material and approval documentation may be as important as electrical performance.

Mechanical connection and installation stress

Thread type, torque, sealing method, port depth, diaphragm exposure, and cable routing can all influence measurement quality. A pressure transmitter installed with excessive torque or poor mechanical alignment may show zero shift. A level probe installed without strain relief may fail mechanically even if the sensing element is accurate. A compact OEM sensor mounted too close to heat sources, vibration, or board stress may drift or lose repeatability.

Where Keller sensors fit in industrial design

Keller sensors are most relevant where pressure measurement is a core function rather than an accessory. Typical application areas include water level monitoring, hydrology, industrial automation, hydraulic control, compressor monitoring, gas measurement, laboratory equipment, mobile machinery, process skids, and OEM instruments.

The strongest fit is usually an application that needs one or more of the following: media-isolated pressure measurement, compact OEM integration, traceable calibration documentation, multiple pressure reference choices, rugged field packaging, or a specialized output format. A weaker fit may be a low-cost consumer device where a board-mounted MEMS pressure sensor is sufficient and direct media contact is not a concern.

There is also a procurement consideration. Keller offers many pressure ranges, housings, outputs, and special variants. That flexibility is useful, but it means selection should be more deliberate than buying a generic module. Engineers should confirm the exact datasheet revision, regional availability, lead time, cable or connector option, calibration requirement, and environmental approval before freezing a bill of materials.

Common mistakes when specifying Keller pressure sensors

• Choosing pressure range without checking spikes. Normal operating pressure is not the same as peak pressure during startup, valve closure, pump pulsation, or fault conditions.
• Confusing absolute and gauge pressure. This can create systematic measurement errors, especially in vacuum, weather, altitude, and gas applications.
• Ignoring temperature compensation. Temperature effects can be larger than the headline accuracy figure in real installations.
• Assuming all stainless-steel packages are chemically compatible. Seals, fill fluids, cables, and diaphragms also matter.
• Overlooking venting in level probes. Vented gauge level measurement can be affected by blocked vent tubes, moisture ingress, or cable damage.
• Selecting a digital output too late. Digital integration should be considered early because it affects firmware, testing, and system diagnostics.
• Using catalogue descriptions as final approval evidence. Critical applications should rely on the latest datasheet, certificates, and supplier confirmation.

Frequently asked questions

Are Keller sensors only pressure sensors?

Keller Pressure is mainly associated with pressure measurement. Its product range includes OEM pressure transducers, pressure transmitters, level probes, digital gauges, and data loggers. Level measurement products typically work by measuring hydrostatic pressure and converting it into a liquid level value.

What is the difference between a Keller pressure transducer and a pressure transmitter?

A transducer is often closer to the sensing element and may require more signal conditioning by the user. A transmitter usually includes signal conditioning and provides a standardized output such as 4–20 mA, voltage, or a digital interface. The exact distinction depends on the product series, so the datasheet should always be checked.

Can Keller sensors be used with water level monitoring?

Yes. Keller offers submersible level probes and related instruments for hydrostatic level measurement. Selection should account for water chemistry, cable material, venting, lightning protection, installation depth, required accuracy, and whether the application involves drinking water, wastewater, groundwater, or surface water.

Do Keller sensors support digital outputs?

Some Keller product families support digital communication or digitally conditioned outputs, including interfaces used in OEM and industrial environments. The correct choice depends on whether the host system needs simple analog measurement, serial data, diagnostics, or integration with an automation network.

What should be verified before selecting a Keller sensor?

Verify pressure range, pressure reference, overload rating, media compatibility, wetted materials, output signal, accuracy definition, temperature behavior, mechanical connection, environmental rating, certificates, and the latest datasheet revision. For safety-critical or regulated systems, written confirmation from the supplier or manufacturer is advisable.