Ultimate Guide to Selecting a Diffused Silicon Pressure Transmitter
Expert guidance for industrial measurement applications
Overview
Pressure transmitters are classified by their sensing technologies, including diffused silicon, ceramic, capacitive, and monocrystalline silicon. Among these, diffused silicon pressure transmitters are the most widely adopted across industries. Known for their robust performance, reliability, and cost-effectiveness, they are ideal for pressure monitoring and control in oil and gas, chemical processing, steel manufacturing, power generation, environmental engineering, and more.
These transmitters support gauge, absolute, and negative pressure measurements—even in corrosive, high-pressure, or hazardous conditions.
But how did this technology develop, and what factors should you consider when choosing the right model?
Origins of Diffused Silicon Technology
In the 1990s, NovaSensor (USA) introduced a new generation of diffused silicon sensors using advanced micromachining and silicon bonding technologies.
The principle is simple but effective: process pressure is isolated by a diaphragm and transferred through sealed silicone oil to a sensitive silicon membrane. On the opposite side, atmospheric pressure is applied as a reference. This differential causes the membrane to deform—one side stretches, the other compresses. Embedded strain gauges detect this deformation, converting it into a precise electrical signal.
8 Key Parameters for Selecting a Diffused Silicon Pressure Transmitter
1. Medium Characteristics
The chemical and physical nature of the process fluid directly impacts sensor compatibility.
Suitable: Gases, oils, clean liquids — typically handled with standard 316L stainless steel sensors.
Unsuitable: Highly corrosive, viscous, or crystallizing media — these may clog or damage the sensor.
Recommendations:
- Viscous/crystallizing fluids (e.g., slurries, syrups): Use flush diaphragm transmitters to prevent clogging.
- Hygienic applications (e.g., food, pharma): Select tri-clamp flush diaphragm models (≤4 MPa for secure fitting).
- Heavy-duty media (e.g., mud, bitumen): Use cavity-free flush diaphragms, with a minimum working pressure of ~2 MPa.
⚠️ Caution: Do not touch or scratch the sensor diaphragm — it is extremely delicate.
2. Pressure Range
Standard measuring range: –0.1 MPa to 60 MPa.
Always choose a transmitter rated slightly above your maximum working pressure for safety and accuracy.
Pressure unit reference:
1 MPa = 10 bar = 1000 kPa = 145 psi = 760 mmHg ≈ 100 meters water column
Gauge vs. Absolute Pressure:
- Gauge pressure: referenced to ambient atmospheric pressure.
- Absolute pressure: referenced to a perfect vacuum.
Note: In high-altitude regions, use vented gauge transmitters (with vent tubes) to compensate for local atmospheric pressure when accuracy matters (
3. Temperature Compatibility
Typical operating range: –20°C to +80°C.
For high-temperature media (up to 300°C), consider:
- Cooling fins or heat sinks
- Remote diaphragm seals with capillaries
- Impulse tubing to isolate the sensor from direct heat
4. Power Supply
Standard supply: DC 24V.
Most models accept 5–30V DC, but avoid inputs below 5V to prevent signal instability.
5. Output Signal Types
- 4–20 mA (2-wire): Industry standard for long-distance and interference-resistant transmission
- 0–5V, 1–5V, 0–10V (3-wire): Ideal for short-range applications
- RS485 (digital): For serial communication and networked systems
6. Process Connection Threads
Common thread types:
- M20×1.5 (metric)
- G1/2, G1/4 (BSP)
- M14×1.5
Match thread type with industry norms and your system’s mechanical requirements.
7. Accuracy Class
Typical accuracy levels:
- ±0.5% FS – standard
- ±0.3% FS – for higher precision
⚠️ Avoid specifying ±0.1% FS accuracy for diffused silicon transmitters. They are not optimized for ultra-precision work at this level. Instead, use monocrystalline silicon models for such applications.
8. Electrical Connections
Choose based on your installation needs:
- DIN43650 (Hirschmann): Good sealing, commonly used
- Aviation plug: Easy installation and replacement
- Direct cable lead: Compact and moisture-resistant
For outdoor use, select 2088-style housing for enhanced weatherproofing.
Special Case Considerations
Q1: Can I measure ammonia gas?
Yes, but only with appropriate materials (e.g., Hastelloy diaphragm, PTFE seals). Also, ammonia reacts with silicone oil—use fluorinated oil as the fill fluid.
Q2: What about flammable or explosive media?
Avoid standard silicone oil. Use fluorinated oils (e.g., FC-70), which offer better chemical stability and explosion resistance.
Conclusion
Thanks to their proven reliability, adaptability, and cost-effectiveness, diffused silicon pressure transmitters remain a go-to solution across diverse industries.
Careful selection based on the medium, pressure, temperature, connection type, and accuracy ensures optimal performance and long-term durability.
Post time: Jun-03-2025