An inline pressure transducer is a compact pressure transmitter that screws directly onto the pipeline via a single threaded interface. The sensitive diaphragm is in close contact with the medium, without manifolds or remote transmission diaphragms. This form factor is most commonly found in hydraulic systems, compressed air mains, cooling water circuits, HPLC process lines, and OEM equipment.
Sino-Inst manufactures and supplies 10 models of its SI series inline pressure transmitters, covering ranges from -100 kPa to 1000 MPa, and media temperatures from -252 °C to +300 °C. They support 4-20 mA, 0-5 V, 0-10 V, RS485, and HART outputs, with ATEX/IECEx explosion-proof options available.
Send us your process range, medium, process interface, and output signal, and our engineers will provide a quote the same day.
Inline pressure transducers are the most common type of transducer used in industrial pressure measurement. They are primarily distinguished from other pressure transmitters by their structure. Based on our experience, inline pressure transducers have three key structural features:
Differences from other common installation methods:
| Form | Key Features: | Is it inline? |
| Differential pressure (DP) | Dual-port capsule + valve manifold | No |
| Flange-mount | Flanged connection, commonly used for tank openings and large diameters | No |
| Submersible / hydrostatic | Long cable + immersion in liquid | No |
| Diaphragm seal with capillary | Remote diaphragm + capillary tube | No |
| Inline screw-mount | Single thread + compact design + welded housing | Yes |
In terms of spelling, “inline,” “in-line,” and “in line” refer to the same thing and can be used interchangeably. However, the terms “sensor,” “transducer,” and “transmitter” are slightly different.
Pressure sensor, pressure transducer, and pressure transmitter correspond to three different stages in the signal chain: the sensing element, the signal conditioning circuit, and the standard loop output. These three terms are often used interchangeably in daily purchasing and our quotations. For accurate differentiation, refer to the “Output Signal” section on the product page:
Below are the inline pressure transducers that Sino-Inst regularly supplies. They are listed in two groups: Standard (for industrial use with clean media at normal temperature) and Extreme-Condition (for special operating conditions). You can select directly.
Inline pressure transducers are primarily used for real-time pressure measurement in industrial liquid, gas, and steam pipelines. Sino-Inst products are commonly used in the following 7 application areas:
Hydraulic Systems
Hydraulic power units, injection molding machines, machine tools, and hydraulic circuits in construction machinery. High pressure (10–700 MPa is common), severe pulsation, and high vibration. Selection should consider fatigue life and vibration immunity indicators. Compact pressure transducers cover standard ranges; the SI-702 high-pressure model is used for testing presses and heavy-duty hydraulic systems.
Compressed Air Mains
Plant compressed air mains, air tanks, air compressor outlets, and before and after filters. The medium is relatively clean but contains oil mist and condensate; the range is typically 0–10 bar / 0–1.6 MPa. Basic silicon piezoresistive transducers like the SI-1180 and Compact can cover most scenarios.
Cooling Water Circuits
Cooling tower return water, process cooling water, condensers, and air conditioning mains. The medium is non-corrosive but contains chloride ions, suspended particles, and algae, making it prone to scaling over time. The SI-1102 ceramic diaphragm is more durable in these conditions, while the SI-1180 is used in loops with better water quality.
OEM Machinery
Installation equipment internal piping pressure monitoring, automation equipment, robotic end effectors, and compact OEM equipment. These scenarios prioritize cost, installation space, and batch consistency. The Compact Pressure Transducer and SI-1180 are the preferred choices for OEM mass production, with customizable ranges and interface specifications.
Process Gas & Semiconductor Lines
Semiconductor high-purity gas piping (N2, O2, H2, Ar), CVD/PVD reaction chamber inlet, and specialty gas distribution. Hydrogen processes require explosion-proof (ATEX/IECEx) protection, and the high-purity medium must be free of metal contamination. Diaphragms can be customized with electropolished 316L or Hastelloy. A common configuration is the SI-1188 explosion-proof type combined with the SI-1185 intelligent RS485 multi-machine co-line solution.
Extremely Low Temperature Liquids and Gases
Gas such as CO2, N2, H2, and HE are mostly at temperatures as low as -60℃, and can even liquefy to -196℃ and -252℃. Most pressure transmitters cannot measure such extreme low-temperature media. Sino-Inst offers the SI-2088 and CPT-20SD1, specifically designed for customized low-temperature media pressure measurement solutions.
Extremely High Temperature Gases and Liquids
Media such as steam, heat transfer oil, and engine exhaust have relatively high temperatures, ranging from 100℃ and 250℃ to as high as 850℃. Conventional pressure transmitters have a media temperature resistance of 85℃. Sino-Inst supports customized high-temperature inline pressure transmitters, with customizable pressure and temperature ranges.
Based on our years of experience in industrial process pressure measurement, we have summarized and compared these installation methods so that you can intuitively choose the appropriate installation method.
| Form | Installation Methods | Suitable Media | Typical Measurement Range | Typical Applications |
| Inline | Single-threaded direct screw-in installation (G / NPT / M20×1.5) | Liquids, gases, steam | -100 kPa~ 1000 MPa | Hydraulic systems, pneumatic systems, cooling water, OEM, HPLC |
| Submersible | Long cable extends from the top, with the sensor submerged in the liquid | Water-based liquids | 0~200 m H₂O (water column) | Well water, fire protection reservoirs, rivers, oil tank liquid levels |
| Sanitary / Tri-Clamp | Clamp connection, flush with the diaphragm, CIP-compatible; | Food, pharmaceutical, and bioprocessing media | Typically 0~6 MPa | Fermenters, filling lines, clean steam |
| Flange-Mount | Flange connection, compatible with a valve manifold; | Tanks, large-diameter pipes | 0~ 60 MPa | Storage tanks, differential pressure flow measurement, filters |
In short, you can choose inline pressure transducers in the following operating conditions:
If the interface on the process line is already a flange or Tri-Clamp, select Flange-Mount or Sanitary accordingly. Do not force the use of inline adapters. Adapters will increase leakage points and pressure loss.
Below are the six hard parameters engineers should align on the RFQ before ordering an inline pressure transducer. Start with the overview table, then walk through the six-step decision logic.
| Parameter | Common options | Engineer’s note |
|---|---|---|
| Range | -100 kPa to 1000 MPa, any standard step | Choose process max × 1.5 and round up to the next step |
| Process connection | G1/4, G1/2, NPT 1/4, NPT 1/2, M20×1.5, M22×1.5 | Specify thread spec plus seal type (O-ring, flat face, conical) |
| Output signal | 4-20 mA, 0-5 V, 0-10 V, RS485, HART | 4-20 mA for long field runs; 0-10 V for OEM board-level; RS485 for multi-drop digital |
| Accuracy class | 0.1% / 0.2% / 0.25% / 0.5% FS | 0.5% is enough for general industrial use; pick 0.1% for custody transfer or calibration standards |
| Ingress / Hazardous area | IP65 / IP67 / IP68; ATEX, IECEx, Ex ia, Ex d | IP65 minimum outdoor; IP68 for submersion; confirm hazardous zone before sizing |
| Media compatibility | 304, 316L, Hastelloy C, ceramic, tantalum, PTFE | Hastelloy for chloride-bearing media; ceramic or tantalum for strong corrosion |
Round up to the next standard step. For example, a process maximum of 35 MPa fits a 40 MPa or 50 MPa transducer with 25-50% headroom. Long-term operation at full scale shortens diaphragm life.
Check what thread the process line uses: G, NPT, or M20x1.5. If the line already has flanged or Tri-Clamp interfaces, do not adapt them to inline; pick the matching Flange-Mount or Sanitary type instead.
Check what input the PLC, DCS, or board accepts. 4-20 mA is the field default for runs of 50 m or more, or for hazardous areas. Use 0-10 V for OEM board-level, RS485 Modbus for multi-drop, and HART for remote configuration and diagnostics.
Indoor use is fine with IP65. Outdoor with rain exposure needs IP67; basins or long-term submersion need IP68. Hazardous areas follow Zone 1/2 classification, mapped to Ex ia or Ex d ratings. Get the area classification drawing from the process engineer before ordering.
For the full 10-point selection framework, see our pillar guide: 10-Point Pressure Sensor Selection Guide.
Looking for the complete pressure sensor guide? Start here: Pressure Sensors & Transmitters: The Complete Guide — main hub covering 7 principles, 5 outputs, and 10 form factors.
Zhang Wei, possesses 20 years of experience as an automation instrumentation engineer, specializing in the research, design, installation, commissioning, and maintenance of automation instruments.
Face to various instrument communication protocols (such as Modbus, Profibus, etc.), with solid hardware circuit design and software programming skills (proficient in C language and PLC programming). Has extensive project experience; projects he has led and participated in have all achieved outstanding results, improving product accuracy, reducing costs, and increasing production efficiency.
Possesses excellent communication and coordination skills and a strong team spirit, enabling him to quickly respond to customer needs and provide high-quality automation instrumentation solutions.
