Pressure sensors are only as good as their calibration. Whether you’re monitoring water depth in a borehole, controlling a process line, or logging tank levels, a well-calibrated sensor is the difference between reliable data and costly guesswork. This guide walks through what calibration actually means, why it matters, and how to do it properly.
What is pressure sensor calibration?
Calibration is the process of comparing your sensor’s output against a known, traceable reference pressure and then adjusting (or documenting) any deviation. In simple terms, you apply a series of known pressures, record what the sensor reports, and correct the difference so the readings match reality.
Every sensor drifts slightly over time due to temperature cycling, mechanical stress, media exposure and ageing of the sensing element. Regular calibration keeps your measurements accurate, repeatable and traceable — essential for compliance, safety and quality.
Key terms to understand first
- Zero (offset): the reading the sensor gives at its baseline pressure (often atmospheric). A zero error shifts every reading up or down.
- Span (gain): the difference between the sensor’s output at its lowest and highest rated pressure. A span error scales the readings.
- Reference standard: a calibrated master gauge or deadweight tester with accuracy typically 4× better than the sensor under test.
- Traceability: proof that your reference standard links back to a national/international standard (e.g. UKAS, NIST).
What you'll need
- A traceable pressure reference (deadweight tester, precision hand pump with master gauge, or a calibrated pressure calibrator)
- A stable power supply and an accurate meter suited to your sensor’s output (mA, V or a digital reader for SDI-12/RS485)
- A controlled, stable temperature environment
- The sensor’s datasheet, showing its pressure range and output type
Step-by-step: calibrating a pressure sensor
- Let everything stabilise. Allow the sensor and reference equipment to reach a stable ambient temperature (often 20 °C ±2 °C). Temperature is one of the biggest sources of error.
- Connect and power up. Wire the sensor to its supply and connect the output to your meter. For analogue devices, read the mA or voltage output; for digital devices, read the value over SDI-12 or RS485.
- Set the zero. With the sensor at its baseline reference pressure, record the output. Adjust the zero so it reads correctly (e.g. 4 mA for a 4–20 mA device).
- Apply full-scale pressure. Using your reference, apply the sensor’s maximum rated pressure and record the output. Adjust the span so full scale reads correctly (e.g. 20 mA).
- Re-check zero and span. Zero and span adjustments interact, so cycle between them until both are within tolerance.
- Verify across the range. Apply several known points — typically 0%, 25%, 50%, 75% and 100% of range — both increasing and decreasing, to check linearity and hysteresis.
- Document everything. Record the applied pressures, sensor readings, deviations and ambient conditions to produce a calibration certificate.
How often should you calibrate?
It depends on the application, but a good starting point is once every 12 months. Increase the frequency for critical, safety-related or harsh-environment installations, and after any event that may have overloaded or damaged the sensor.
Tips for accurate, repeatable results
- Always use a reference standard significantly more accurate than the sensor under test.
- Keep the calibration environment thermally stable and allow adequate warm-up time.
- Approach each test point from the same direction where possible to minimise hysteresis effects.
- Check the media compatibility — calibrating with a different medium (air vs. water) can matter for some sensors.
Choosing sensors that make calibration easy
Starting with a high-quality, well-characterised sensor makes calibration far simpler. Stork Solutions’ submersible level sensors and transmitters are built on pressure-sensing technology and supplied with clear datasheets covering output type and pressure range — exactly the information you need to calibrate confidently.
For analogue installations, the SLS-SA (silicon, analogue output) and SLS-CA (ceramic, analogue output) support mV, 4–20 mA, 0.5–4.5 V and 0–10 V outputs, making them straightforward to calibrate with a standard meter.
If you’re working with digital systems, the SLS-SD (silicon, digital output) and SLS-CD (ceramic, digital output) provide SDI-12 and RS485 outputs, allowing you to read calibrated values directly in engineering units.
Need help?
If you’re unsure which sensor suits your application, or you’d like guidance on calibration and output configuration, get in touch with the Stork Solutions team — we’re happy to help you get accurate, reliable measurements from day one.
