High Pressure Transducer Selection: Range, Proof & Sealing

A lead engineer hands you a line that sits at 20,000 psi and spikes higher every time a valve slams shut. The hard part is not finding a transducer that reads that number. The hard part is choosing four things together so the instrument survives the service: the full-scale range, the proof and burst margins above it, the sealing and process connection, and the sensing technology under the diaphragm.

For hydrogen service, where the diaphragm must also resist permeation and embrittlement, see the hydrogen pressure transducer guide.

If the service is hot as well as high-pressure, our high-temperature pressure transducer guide covers the temperature derating and mounting options that keep the sensor alive.

Get one of the four wrong at high pressure and the transducer either drifts within months or fails outright. This guide takes the four decisions in the order you actually make them on a data sheet.

Why high pressure breaks standard transducers

A transducer that works at 100 psi can fail quickly at 20,000 psi, for reasons that have nothing to do with its accuracy rating. At high pressure the diaphragm carries large stress on every cycle, so fatigue and slow zero drift, rather than a one-time over-range event, become the failure modes that matter.

An oil-filled sensor is a good example. The same fill that protects a low-range device now has to transmit very large forces without leaking or compressing non-linearly. Elastomer seals that hold gas at moderate pressure begin to extrude or take a set.

In the field on refinery hydraulic and test-stand lines, I have seen one failure pattern more than any other. A transducer specced at 100 percent of span reads fine on commissioning, then returns a drifting zero a few months later, because nothing left any headroom for the spikes. The selection problem at high pressure is really a durability problem, and durability comes from range headroom, sealing, and sensor construction, not from the catalog accuracy figure.

Range, proof, and burst pressure defined

Three numbers describe how much pressure a transducer takes, and they mean different things. The measuring range (full scale, or FS) is the span the device converts to its output, and it is the only one of the three the device is calibrated against.

The proof pressure, also called over-range, is the maximum you can apply without permanently shifting the calibration. The device may read off-scale while it is there, but it returns to spec afterward. The burst pressure is the point at which the wetted parts mechanically fail and leak.

Typical industrial transducers carry proof at about 1.5 to 2 times FS and burst at about 3 to 5 times FS, though the exact multiples vary by construction, so read them from the data sheet rather than assume. The over-range and burst terms follow the process-transmitter test practice defined in IEC 60770:2010 (Part 1). Proof and burst are specified separately, and a high proof rating does not imply a high burst rating.

For reference, the HMK HM28 sapphire transmitter carries an overload capacity of 2 times full scale on its standard ranges. The number that protects you in the field is proof pressure, because your transient spikes have to stay under it.

Sizing the range to the peak, not the static

The most common high-pressure mistake is sizing the range so the normal operating pressure equals full scale, which leaves no headroom for the spikes a high-pressure system always produces. A better rule is to size the range so the maximum sustained pressure sits near 70 to 80 percent of FS, and the worst-case transient stays below proof pressure with margin.

Take a hydraulic press line. It sits statically at 20,000 psi and sees water-hammer transients to about 28,000 psi when a directional valve closes.

Pick a 0–20,000 psi unit and the gauge reads at 100 percent of span all the time, which is poor for accuracy and fatigue, while a proof of 1.5 times FS (30,000 psi) only barely clears the 28,000 psi spike. Pick a 0–35,000 psi unit instead. The static pressure now sits at 57 percent of span. The spike lands at 80 percent and never becomes an over-range event, and proof at 1.5 times FS is 52,500 psi with comfortable margin.

The dimensional check is simple: confirm that *peak transient ≤ proof pressure* and that *sustained pressure ≤ 0.8 × FS*, both in the same units, before you lock the range. This is also why running any transducer at the top of its range is a poor idea; for the accuracy side of that trade-off, see our note on turndown ratio and accuracy. Pure transient survival, such as repeated hydraulic shock, is a separate topic, covered in hydraulic pressure transducer selection.

Sapphire and thin-film beat oil-filled silicon

At high pressure the sensing element decides how the transducer ages. Oil-filled diffused-silicon sensors give excellent low-range performance, but the silicon die and the oil fill behind a thin isolation diaphragm work hard at high pressure, and fast events or overload can shift their zero over time. A stiffer, fatigue-resistant element handles high static pressure and repeated overload better.

Sensing element	High-pressure strength	Overload / fatigue	Best fit
Mono-crystalline sapphire (HM28)	To 260 MPa / 37,700 psi	Zero hysteresis, no creep or fatigue, 2× FS overload	High static & hydraulic pressure
Thin-film on steel	High	Strong fatigue life	High-pressure OEM & test
Ceramic (HM23Y)	To 220 MPa / 31,900 psi	Robust, anti-clogging	Dirty / downhole media
Oil-filled diffused silicon	Limited at top ranges	Zero can shift on fast events	Cleaner, lower-range duty

A mono-crystalline sapphire element is the strongest answer here. Sapphire is far harder than silicon, shows zero hysteresis, and does not creep or fatigue under load, which is why it holds calibration at the top of the scale.

The HMK HM28 uses a German mono-crystalline sapphire sensor bonded to a titanium diaphragm. It reaches 260 MPa (37,700 psi) at ±0.1% FS, with ±0.1% FS per year long-term stability, across media from −65 °C to +200 °C. If your ranges are quoted in MPa or bar, our MPa to PSI converter makes the cross-check quick.

Thin-film-on-steel sensors, which bond a foil strain gauge to a steel diaphragm, are another durable choice in this band. In practice, for genuine high pressure with overload events, weight the choice toward sapphire or thin-film, and keep oil-filled silicon for cleaner, lower-range duty. If you are still sorting out sensor, transducer, and transmitter, our terminology guide explains the terms.

Connections rated for the pressure band

The process connection and its seal are rated independently of the sensor, and at high pressure they are often what limits the whole assembly. As a rough field guide, threaded ports with elastomer O-ring face seals work up to the low tens of thousands of psi in clean liquid service. Their reliability drops under high-cycle duty and gas service, as the elastomer extrudes or takes a set.

Above that band, all-metal sealing is the safer call. The options are welded diaphragms with no internal elastomer, metal-to-metal cone-and-thread fittings of the high-pressure type, autoclave-style connections, or code-rated flanges.

The HM28 uses an all-welded titanium-and-sapphire wetted stack with no internal O-ring at the sensor, which is what lets it run to 260 MPa without a seal that creeps. Match the connection rating to the same peak-transient number you used to size the range, and confirm the thread standard separately; our guide on NPT versus G/BSP threads covers that choice. The rule of thumb: elastomer for moderate clean-liquid duty, all-metal welded or cone-and-thread for the high bands, gas, and high-cycle service.

Media that change the call: hydrogen and gas

Some media override the range and connection logic above. High-pressure gas stores far more energy than liquid at the same pressure, so a failure is more violent, and case venting and burst margin matter more. Gas also decompresses quickly, which can damage oil-filled sensors whose fill cannot follow a fast pressure drop.

Hydrogen is the sharpest example. At the 350 to 700 bar pressures used in hydrogen fueling, hydrogen permeates seals and embrittles certain steels, so wetted-material selection stops being a formality and becomes the deciding factor.

Components for this service are qualified to standards such as ISO 19880:2018 (Part 3) and SAE J2579, which set the material and pressure-cycle requirements that a transducer placed on a fueling line has to meet before it ever sees service. All-metal wetted parts in a hydrogen-compatible alloy, and in some designs a protective coating, are what keep the sensor stable and safe. If your service is high-pressure hydrogen or fast-cycling gas, confirm material compatibility with the manufacturer before you commit to a range or a sensor technology.

For sour oilfield service with H₂S, wetted materials follow NACE MR0175 / ISO 15156:2020. For viscous or clogging media at high pressure, a flush or extended diaphragm changes the call again; see flush-mount transducer selection.

On sour (H₂S) service the wetted-material rules tighten — see NACE MR0175 sour-service material selection for pressure transmitters.

Matching HMK transducers to your pressure band

Once range, proof margin, sensing technology, and connection are settled, the product usually falls out of the pressure band and the media. For high static and hydraulic pressure up to 260 MPa (37,700 psi) in clean to moderately aggressive media, the all-welded sapphire HM28 is the core choice, at ±0.1% FS with 2× overload.

For downhole oilfield, mining, and well service to 220 MPa (about 31,900 psi), where the media is dirty or clogging, the ceramic-sensor HM23Y is built for anti-clogging duty at ±0.25% FS. Both offer a 4-20 mA loop output, and the HM28 also gives 1-5 V, 0-5 V, and 0-10 V voltage signals when the loop is not the requirement.

The concrete next step is to write down three numbers before you call a supplier: your sustained operating pressure, your worst-case transient, and the media. Then size full scale so the sustained value sits near 70 to 80 percent of span and proof pressure clears the transient. With those three numbers you can request a quote that matches the service. Browse the full range on the pressure transmitters category, or send the three numbers to our engineers for a sizing check.

Frequently Asked Questions

What does a high pressure transducer do?

It converts a high pressure, usually thousands to tens of thousands of psi, into a standard electrical signal such as 4-20mA or 0-5V that a controller or display can read. The high pressure part refers to the range, and to the reinforced diaphragm, sealing, and sensor construction needed to survive it.

What is the maximum pressure a transducer can measure?

Industrial transducers reach roughly 200 to 260 MPa (about 30,000 to 38,000 psi) in standard catalog products. The HMK HM28 sapphire unit, for example, covers up to 260 MPa (37,700 psi). Specialized laboratory and dynamic devices go higher, but the connection and sealing become the limiting parts.

What is the difference between proof pressure and burst pressure?

Proof pressure is the maximum you can apply without permanently shifting the calibration; the device recovers to spec afterward. Burst pressure is where the wetted parts mechanically fail and leak. Size your range so transients stay under proof, and treat burst purely as a safety margin.

How do I test a high pressure transducer?

Apply known pressures from a deadweight tester or a calibrated high-pressure reference at several points across the range. Compare the output against the reference at each point, including a return to zero. Never exceed the proof pressure during the test, and use connections and tubing rated for the test pressure.

Can a pressure transducer measure high-pressure hydrogen?

Yes, but only with hydrogen-compatible wetted materials. At 350 to 700 bar,