Ceramic capacitive pressure sensors are widely used in industrial automation, process control, water treatment, chemical, and many other industries due to their ruggedness, corrosion resistance, high stability, and high accuracy. The core principle uses a ceramic diaphragm as one plate of a capacitor. When pressure is applied to the diaphragm, it deflects slightly, causing a change in capacitance. A measuring circuit then converts this capacitance change into a standard electrical output signal.
Key Selection Factors
1. Media Compatibility
This is the primary selection factor. Ceramic material itself offers excellent corrosion resistance and can withstand most corrosive liquids and gases, including acids and alkalis. When selecting, confirm that the parts in contact with the media (mainly the ceramic diaphragm) can operate reliably over the long term. For high‑viscosity or easily crystallized media, a flush‑diaphragm (flat film) design effectively prevents clogging.
2. Pressure Range
Select the range based on the maximum pressure in your actual operating condition. To ensure sensor safety and extend service life, it is generally recommended that the working pressure be between 60% and 80% of the sensor's full scale, leaving some overpressure margin. Ceramic capacitive sensors typically have strong overload capability and can withstand 2× or even higher full‑scale pressure without damage.
3. Accuracy
Accuracy is a critical performance indicator, usually expressed as a percentage of full scale (%FS), and includes errors due to non‑linearity, hysteresis, and repeatability. The combined accuracy of ceramic capacitive pressure sensors is generally between 0.2%FS and 0.5%FS. For applications requiring precise control and measurement, a model with higher accuracy should be selected.
4. Operating Temperature Range
The sensor must operate stably within a specific ambient temperature range. Ceramic material itself has good thermal stability and a wide operating temperature range, typically from -40°C to +135°C. When selecting, verify that the sensor's temperature compensation range covers the actual operating conditions to avoid measurement drift caused by temperature changes.
5. Output Signal
Choose the appropriate output signal according to the input requirements of your control system (e.g., PLC, DCS, microcontroller). Common standard signals include:
Analog outputs: 4‑20 mA (two‑wire, strong anti‑interference capability, most common), 0‑5 V, 0‑10 V.
Digital outputs: RS485, CAN, etc., which are convenient for building intelligent networks.
6. Process Connection & Electrical Connection
Process connection: The mechanical connection method between the sensor and the measured medium. Common types include threaded connections (e.g., G1/4, M20×1.5, NPT1/4) and flange connections. It must match the field pipe or equipment interface.
Electrical connection: The way the sensor's electrical signals are brought out. Common types include a Hirschmann connector, aviation plug, and direct cable exit. Choose the type that facilitates field wiring and maintenance.
7. Ingress Protection (IP) Rating
Select the appropriate IP rating based on the humidity and dust conditions of the installation environment. For outdoor or humid environments, an IP65 or IP67 sensor should be chosen to prevent moisture and dust ingress that could cause damage.
Key Technical Parameters
| Parameter | Typical Specification |
|---|---|
| Measuring Medium | Sulfuric acid |
| Pressure Range | 0 ~ 10 MPa gauge pressure |
| Combined Accuracy | ±0.25%FS |
| Long‑Term Stability | < 0.25%FS / year |
| Medium Temperature | 110°C |
| Output Signal | RS485 |
| Pressure Interface | Large Hirschmann connector |
| Power Supply Voltage | 24 VDC |
