Choosing the right pressure transmitter for industrial fluids and gases requires more than matching a pressure range to a process setpoint. The transmitter becomes part of the pressure boundary, the electrical loop, and the physical installation. Its sensing technology must suit the media, its wetted materials must resist chemical and thermal exposure, and its output must integrate correctly with the control system.
A transmitter that performs reliably with clean compressed air may be unsuitable for hydraulic oil, corrosive chemicals, viscous food products, or high-temperature fluids. A dependable selection process should evaluate sensing technology, pressure range, pressure reference, wetted materials, output signal, process connection, accuracy, temperature, vibration, ingress protection, and hazardous-area requirements.
Diversified Technologies offers industrial pressure sensors and switches for a wide range of liquid, gas, vacuum, hydraulic, and hygienic applications.
1. Match the Sensing Technology to the Media
A ceramic pressure transmitter is often a strong choice for water, fuels, oils, hydrostatic level measurement, and selected chemically demanding fluids. Ceramic aluminum oxide diaphragms provide stable low-pressure measurement and broad media resistance. The PTC 350 Ceramic Pressure Transmitter, for example, uses capacitive ceramic sensing for ranges from 40 mbar to 20 bar.
Piezoresistive sensors provide high sensitivity and fast response in many low-pressure applications. A non-isolated design may be limited to clean gases or approved oils, while an isolated metallic diaphragm separates the media from the sensing chip.
For extreme hydraulic service, a welded thin-film design can reduce leak paths and withstand pressure cycling, vibration, and shock. For sticky, crystallizing, or hygienic products, a flush diaphragm pressure transmitter minimizes dead space and product buildup.
2. Select the Correct Pressure Range and Reference
Choose the range from actual operating data. Document normal and maximum pressure, startup conditions, pump pulsation, valve-closure spikes, water hammer, vacuum events, and credible abnormal conditions.
The selected range must withstand expected transients without being so wide that normal pressure occupies only a small portion of the signal. Because accuracy is commonly stated as a percentage of span, an oversized range increases the possible error in engineering units. A ±0.5% span transmitter represents ±0.05 bar on a 10-bar range but ±0.5 bar on a 100-bar range.
Select the correct pressure reference:
- Gauge pressure for most hydraulic, pneumatic, pump, and vented-vessel systems
- Absolute pressure when atmospheric changes must not affect the reading
- Vacuum or compound pressure when the process operates below atmospheric pressure
- Differential pressure between two pressure points
A differential pressure transmitter may be required for filter monitoring, flow measurement, or pressure-drop measurement.
Review proof pressure separately from burst pressure. Proof pressure is a survivable overload; burst pressure is a structural safety limit and should never be treated as a normal operating target.
3. Verify Every Wetted Material
A “stainless steel transmitter” may still contain elastomer seals, ceramic components, or filling fluid. Every wetted component—including the port, diaphragm, seals, and welds—must be compatible with the media, additives, cleaning agents, and contaminants.
Common options include:
- 316L stainless steel for general industrial liquids and gases
- 17-4 PH stainless steel for demanding hydraulic applications
- Ceramic aluminum oxide for low-pressure measurement and media resistance
- Hastelloy C-276 for selected corrosive applications
- PP or PVDF for certain aggressive fluids
- FKM, EPDM, NBR, or FFKM seals for different media and temperatures
Seal compatibility deserves particular attention. An elastomer that works with hydraulic oil may deteriorate in another fluid or at a different operating temperature.
This distinction is especially important with a non-isolated low-pressure transmitter. The PTS 345 uses stainless steel construction but is intended for compatible gases and non-aggressive, low-viscosity oils. Housing material alone does not establish universal media compatibility.
4. Match the Output to the Control System
The transmitter output must match the PLC, industrial controller, process display, or data-acquisition system.
A 4–20 mA pressure transmitter is usually the safest industrial default. Current loops work well over long cables and resist electrical interference. The 4 mA live-zero signal also helps distinguish zero pressure from a failed loop.
A 0–10 V output can be appropriate for compact machinery with short, well-routed cables and compatible analog inputs. Before ordering, confirm the supply voltage, input impedance, cable length, grounding, shielding, connector pinout, and response time.
5. Evaluate the Process Connection and Installation Environment
Confirm the process thread or hygienic connection, sealing method, installation torque, orientation, tool clearance, and service access. Avoid transferring heavy hose loads, pipe strain, or unsupported fittings directly into the transmitter. Pulsating systems may require a snubber, while hot processes may need a siphon, cooling element, or remote seal.
Evaluate temperature, condensation, freezing, washdown, dust, outdoor exposure, vibration, shock, and electromagnetic interference. Select enclosure and connector protection for conditions at the transmitter.
Hazardous-area installations require the entire measurement loop to be compatible, including the transmitter, intrinsic safety barrier, wiring parameters, grounding method, area classification, and temperature class.
Hygienic systems may also require crevice-free connections, approved filling fluids, and CIP/SIP compatibility. When pressure is used for a local alarm or shutdown, an electronic pressure switch can complement the continuous transmitter signal.
6. Balance Accuracy, Stability, and Response Time
Reference accuracy is only one part of field performance. Also compare repeatability, thermal error, drift, response time, overpressure capability, and recalibration requirements.
Convert percentage-of-span accuracy into the engineering units used by the process. A tighter specification may be justified for dosing, testing, or closed-loop control, while a wider tolerance may be adequate for general monitoring or alarms.
Temperature effects can exceed room-temperature reference error. When the process operates across a broad temperature range, review thermal error or total error band.
Fast response is useful for hydraulic testing and transient analysis. Stable or damped measurement may be preferable for tank pressure or hydrostatic level measurement. A digital pressure gauge can support field verification.
Our engineers can help you identify the best sensor for your application, whether you’re designing a new system or replacing an existing transmitter. Get expert recommendations based on your pressure range, media, output signal, environmental conditions, and budget.
Comparing Four Pressure Transmitters
| Product | Technology and pressure range | Output options | Best fit |
|---|---|---|---|
| PTC 350 Ceramic Pressure Transmitter | Capacitive ceramic; 0.04–20 bar | 4–20 mA; optional 0–10 V | Low-pressure fluids, fuels, oils, and hydrostatic level |
| PTS 345 Industrial Low Pressure Transmitter | Non-isolated low-pressure sensor; −1,000 to +1,000 mbar | 4–20 mA or 0–10 V | Clean gases, air, vacuum, HVAC, and approved oils |
| PTS 330 High Pressure Industrial Pressure Transmitter | Welded thin-film sensor; 600–2,200 bar | 4–20 mA; optional 0–10 V | Extreme hydraulics, pumps, manifolds, and test stands |
| PTS 310F Hygienic Flush Diaphragm Pressure Transmitter | Flush metallic diaphragm; 0.1–40 bar | Current and voltage options | Food, beverage, pharmaceutical, and viscous media |
PTC 350: Low-Pressure Fluids and Level Measurement
The PTC 350 low-pressure ceramic transmitter is designed for ranges from 40 mbar to 20 bar. Its ceramic aluminum oxide diaphragm supports water, fuel, oil, plant engineering, laboratory equipment, and hydrostatic level measurement.
Configurations include 4–20 mA and optional 0–10 V outputs, material options, and intrinsically safe versions.
PTS 345: Air, Gas, Vacuum, and Very Low Pressure
The PTS 345 industrial low-pressure transmitter covers ranges from −1,000 to +1,000 mbar. It is suited to plant equipment, HVAC systems, gas monitoring, vacuum control, and approved low-viscosity oils.
It offers 4–20 mA and 0–10 V outputs, stainless steel construction, and optional intrinsic safety. Because the sensing design is not media-isolated, confirm compatibility with the exact gas or liquid before ordering.
PTS 330: Extreme Hydraulic Pressure
The PTS 330 high-pressure industrial pressure transmitter uses a welded thin-film sensor for gauge-pressure ranges from 600 to 2,200 bar. Its measuring assembly contains no media-wetted seals, making it a strong option for high-pressure pumps, hydraulic power units, test equipment, manifolds, commercial vehicles, and heavy machinery.
Review pressure spikes, port geometry, fluid compatibility, proof pressure, and burst pressure before specifying this transmitter.
PTS 310F: Hygienic and Viscous Process Media
The PTS 310F hygienic flush diaphragm pressure transmitter covers ranges from 0.1 to 40 bar. It is designed for food, beverage, dairy, pharmaceutical, fermentation, and other clean-process systems.
Its flush, welded diaphragm reduces dead space and residue buildup with viscous or crystallizing products. Hygienic connections, CIP/SIP capability, and optional configurations support demanding installations.
Pressure Transmitter Selection Checklist
Before requesting a quote, document:
- Process fluid or gas, including contaminants and additives
- Normal, maximum, and transient pressure
- Gauge, absolute, vacuum, compound, or differential reference
- Media and ambient temperature
- Wetted-material and seal requirements
- Process connection and electrical connector
- Required accuracy and response time
- 4–20 mA, 0–10 V, or digital output
- Cable length, supply voltage, and controller input
- Vibration, washdown, ingress, and hazardous-area conditions
- Calibration and maintenance expectations
Providing this information helps an applications engineer evaluate the complete process requirement rather than selecting a transmitter based on pressure range alone.
Frequently Asked Questions
Can One Pressure Transmitter Measure Both Liquids and Gases?
Sometimes. The range and output may work for both, but every wetted component must be compatible with each medium. Non-isolated sensors are often limited to clean gases or specifically approved liquids.
Should I Choose 4–20 mA or 0–10 V?
Choose 4–20 mA for long cable runs, electrically noisy installations, and standard process-control loops. Choose 0–10 V for short cable runs in compact equipment with compatible voltage inputs and controlled grounding.
When Is a Flush Diaphragm Necessary?
Use a flush diaphragm for viscous, sticky, crystallizing, hygienic, or easily clogged media. It reduces dead space, limits residue accumulation, and simplifies cleaning.
What Is the Difference Between a Pressure Transmitter and a Pressure Switch?
A pressure transmitter produces a continuous measurement signal. An electronic pressure switch changes its output state at a configured setpoint. Some models also provide an analog output.
Can a Pressure Transmitter Be Used for Tank-Level Measurement?
Yes. In hydrostatic level measurement, the transmitter measures the pressure created by a column of liquid. The pressure range must account for liquid density and the maximum expected level.
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