The negative pressure sealing tester is a key equipment for evaluating the sealing performance of packaging containers, and its calibration directly affects the accuracy and reliability of the test results. The following is the systematic calibration process and core points:

1、 Preparation before calibration

1. Standard equipment configuration

Select standard leak holes certified by metrology (such as glass capillary tubes or laser drilled metal sheets) to cover the full range of the tested equipment;

Equipped with high-precision digital pressure gauges (resolution ≥ 0.1% FS), temperature sensors, and humidity controllers for environmental parameter monitoring.

2. Environmental condition control

The calibration environment should maintain a constant temperature (23 ± 2 ℃) and humidity (50% ± 5% RH) to avoid airflow disturbance;

Stay away from electromagnetic interference sources to ensure stable signal transmission.

3. Equipment status pre check

Check the appearance of the instrument for any damage and the pipeline for any aging or cracking;

Confirm that the oil level of the vacuum pump is normal and the filter is clean and unobstructed;

Initialize device software and reset historical data to avoid memory effects.

2、 Reference pressure calibration

1. Zero point calibration (unloaded state)

Close all testing interfaces and start the vacuum pump to extract the maximum vacuum degree;

Observe whether the instrument display value returns to zero. If there is any deviation, correct the zero point error through software;

This step eliminates the influence of inherent residual pressure in the system on subsequent measurements.

2. Linear verification of measuring range

Gradually connect standard leakage holes of different specifications, corresponding to 10%, 50%, and 90% range points respectively;

Record the deviation between the instrument display value and the nominal value of the standard leak hole, and draw a calibration curve;

The indication error of each point should be ≤ ± 1% FS, and the nonlinearity should be ≤ 0.5% FS.

3、 Dynamic response calibration

1. Speed stability test

Inject compressed air into the testing chamber at the rated rate and monitor the rate of pressure rise;

Repeat three times and take the average, with a fluctuation range of<± 0.2%/s;

Ensure that the equipment can maintain a stable pressure rate under different loads.

2. Pressure attenuation test

After sealing the test chamber, cut off the gas source and start timing;

Continuously record the pressure decay curve within 1 minute;

The qualification standard is that the pressure loss is ≤ 0.5% of the initial value, reflecting the airtightness of the system.

4、 Special condition calibration

1. Temperature compensation calibration

Place the instrument in a temperature control box and repeat range calibration at extreme temperatures of -10 ℃ and 40 ℃ respectively;

Establish a temperature pressure compensation coefficient table and embed equipment algorithms to achieve automatic correction.

2. Adaptation and calibration of irregular workpieces

Customize specialized adapters for irregular containers such as hoses and shaped bottles;

Use 3D printing to simulate the mold and verify the consistency of sealing effect under different contact areas.

5、 Calibration result judgment and adjustment

1. Data review

Comparing the original calibration certificate with the measured data, any out of tolerance items need to be traced back to sensor drift or mechanical wear;

Perform segmented multi-point calibration on non-conforming points and locate abnormal intervals.

2. Hardware adjustment

Adjust the opening of the proportional valve to correct the flow characteristics;

Replace the aging sealing ring to improve the airtightness of the system;

Upgrade firmware algorithm to optimize PID control parameters.

6、 Calibration cycle and records

1. Periodic requirements

New machines must be calibrated before use;

Daily use, daily power on self-test, and comprehensive calibration every month;

Re calibrate after major repairs or replacement of core components.

2. Archive management

Save the original calibration records, standard instrument certificates, and adjustment logs;

Electronic archiving facilitates tracing the historical status of equipment.

Through a standardized calibration process, the measurement accuracy of the negative pressure sealing tester can be ensured to meet the requirements of standards such as ASTM E96 and GB/T 15171, effectively avoiding the risk of misjudgment caused by equipment deviation. It is recommended that enterprises establish a three-level calibration system (daily verification, quarterly precision calibration, annual traceability), combined with preventive maintenance plans to extend the service life of equipment.