The calibration of gauge pressure sensors is the foundation for reliable measurement values in process, test, and automation applications. DDM Sensors performs calibration in the laboratory using traceable standards and documents the results as a factory or accredited calibration. For technical decision-makers, reference to ambient pressure, measurement deviation, hysteresis, drift, and measurement uncertainty are particularly relevant.
The Importance of Precise Pressure Measurement
Gauge pressure sensors measure pressure relative to ambient pressure. Even minor deviations can affect control quality, process stability, and quality assurance.
- Process Reliability: Deviating pressure values lead to incorrect switching and control points.
- Proof of Quality: Reproducible measurement values are required for test benches, production, and end-of-line testing.
- Auditability: Documented calibration results support internal and external proof of compliance, such as ISO 9001.
- System Availability: Early detection of drift reduces unplanned downtime and rework.
Fundamentals of Gauge Pressure Sensor Calibration
Calibration means comparing the unit under test (UUT) with a traceable reference standard under defined conditions. Adjustment is distinct from this: it actively intervenes in the sensor to correct zero point and span.
For gauge pressure sensors, reference to ambient pressure is metrologically decisive. Therefore, environmental conditions, mounting position, preloading against mechanical settling effects, and pressure supply must be kept stable during calibration.
Key parameters include:
- Measurement Deviation: Difference between the displayed value and the reference value.
- Hysteresis: Difference between ascending and descending measurement series.
- Drift: Long-term change in measurement behavior.
- Measurement Uncertainty: Overall evaluation of uncertainty contributions from reference, setup, and ambient conditions.
Required Equipment for Calibration
- Unit Under Test (UUT): The gauge pressure sensor to be calibrated, ideally with full type designation, connection type, and, if applicable, a decontamination declaration.
- Reference Standard: A pressure calibrator or other traceable reference system with a sufficient accuracy ratio, typically evaluated via TUR/TAR.
- Pressure Generation: Hand pump, pressure regulator, or programmable pressure controller for stable and reproducible pressure points.
- Data Acquisition: Multimeter, process calibrator, or suitable acquisition unit to record the output signal.
- Ambient Measurement Technology: Thermometer and barometer to monitor temperature and atmospheric pressure.
- DDM Special Service: Calibration across wide temperature ranges from −40 °C to +150 °C.
- Test Line: Tight connection elements, adapters, and suitable seals for a leak-free setup.
The Gauge Pressure Sensor Calibration Process at DDM Sensors
Step 1: Preparation of the Test Setup
- Calibration Site: We select a stable laboratory environment with controlled temperature and pressure conditions.
- Acclimation: The UUT is thermalized before starting so that thermal transitions and preloading effects do not distort results.
- Visual Inspection: We inspect the sensor, connection, and housing for damage, contamination, and abnormalities.
- Cleaning and Documentation: If required, we review the decontamination declaration and prepare the UUT for laboratory operation.
- Electrical Connection: The sensor is connected to the evaluation unit according to its output signal.
- Warm-up Phase: Before measuring, we allow the system to stabilize to obtain reproducible values.
Step 2: Conducting the Measurement Series
- Test Setup: We connect the UUT, reference standard, and pressure generation into a leak-tight test line.
- Zero-Point Check: Under ambient pressure, we verify the zero-point reference of the gauge pressure sensor.
- Test Points: Next, we approach defined points across the measuring range, typically 0, 25, 50, 75, and 100%.
- Measurement Direction: We record ascending and descending measurement series to evaluate hysteresis and repeatability.
- As-Found Documentation: Values prior to any potential adjustment are logged as “As-found”.
- Stabilization: At each test point, we observe the necessary settling times before taking readings.
Step 3: Evaluation and Adjustment
- Deviation Calculation: We compare UUT values with the reference standard and calculate measurement deviation per test point.
- Specification Comparison: Results are evaluated against manufacturer specifications and internal tolerance limits.
- Adjustment Decision: If the sensor is adjustable and deviation requires it, we perform zero/span adjustment.
- As-Left Documentation: Following adjustment, we repeat the measurement and log final values as “As-left”.
- Calibration Certificate: Finally, we generate the calibration certificate including relevant measurement and ambient data.
Important Influencing Factors and Best Practices
- Ambient Conditions: Temperature, atmospheric pressure, and humidity impact measurement results and must remain stable.
- Reference Standard: Accuracy and long-term stability of the reference system are critical to calibration validity.
- Mounting Position: Installation orientation can affect measurements, especially in sensitive measuring cells.
- Pressure Supply: Fluctuations in pressure generation directly impact repeatability.
- Measurement Signal: Clean capture of the output signal is a prerequisite for reliable evaluation.
- TUR/TAR: The accuracy ratio between reference and UUT must fit the required measurement task.
Calibration Certificates and Metrological Traceability
Function and Necessity of a Calibration Certificate
A calibration certificate documents measurement results, reference standards used, and ambient conditions. It serves as proof for audits, internal quality assurance, and tracking measurement accuracy over the sensor’s lifecycle.
A factory calibration certificate is sufficient for many industrial applications where documented testing according to internal or manufacturer procedures is required. Accredited calibration according to DAkkS / ISO 17025 is necessary when formal traceability and an accredited environment are mandated.
Traceability to National Standards
Metrological traceability describes the unbroken chain from the UUT through reference standards up to national standards. Accredited laboratories secure this chain through defined procedures, documented uncertainties, and monitored measuring equipment.
For the user, this means your reference standard remains dependable when calibrated regularly and transparently. This enables consistent system evaluation and audit-ready operation.
Calibration Services for Gauge Pressure Sensors by DDM Sensors
DDM Sensors offers gauge pressure sensor calibration in its in-house laboratory. We perform factory calibrations according to ISO 9001 as well as accredited calibrations according to ISO 17025.
- Factory Calibration: Documented testing with practical evaluation for industrial applications.
- Accredited Calibration: Traceable calibration with formal proof in an accredited environment.
- Temperature Range: Upon request, we calibrate at temperatures ranging from −40 °C to +150 °C.
- Turnaround Time: Typically approx. two weeks.
- Service Scope: No on-site service available.
Get Expert Advice on Gauge Pressure Sensor Calibration Today
Do you need support calibrating gauge pressure sensors, selecting the right reference setup, or evaluating a calibration certificate? Our engineers are ready to advise you on technical execution, traceability, and the ideal lab service for your application.
Frequently Asked Questions About Gauge Pressure Sensor Calibration
How often should a gauge pressure sensor be calibrated?
A practical guideline is an interval of 12 months. In cases of overload, noticeable drift, repair, or critical applications, event-driven recalibration is recommended.
What is the difference between calibration and adjustment?
Calibration determines the sensor’s deviation from a reference standard without altering the sensor. Adjustment actively intervenes to correct zero point and span. Following an adjustment, measurement must be re-verified.
What do As-found and As-left mean?
“As-found” refers to condition and measurement values prior to adjustment. “As-left” describes values after adjustment and final testing. Both datasets are essential for evaluating sensor stability.
When is accredited calibration necessary?
Accredited calibration is recommended when formal traceability, audit-ready documentation, or customer specifications require it. It provides a higher level of proof than standard factory calibration.