How to Determine if a Thermal Mass Flow Meter Requires Calibration??

How to Determine if a Thermal Mass Flow Meter Requires Calibration??

The need for calibrating a thermal mass flow meter depends on usage conditions, performance changes, and industry standards. The following methods can help assess whether calibration is necessary:

I. Routine Inspection and Performance Anomalies?

Abnormal Measurement Data?

Flow readings deviate by more than ±1% (or ≤±0.5% for high-precision applications) from historical data or standard values.

Zero drift (non-zero reading when no flow is present) or unstable span response.

Changes in Environmental or Operational Conditions?

Significant changes in gas composition, temperature, or pressure (e.g., increased humidity, corrosive media).

Prolonged exposure to extreme environments (high temperatures, dust, vibration).

II. Time-Based and Usage Triggers?

Scheduled Calibration Intervals?

General industrial applications: Calibrate every 6 months to 1 year.

High-precision or high-risk scenarios (e.g., trade settlement, chemical safety): Shorten to 3–6 months.

Impact of Usage Frequency?

After continuous or high-frequency operation (e.g., exceeding 2,000 cumulative operating hours), calibration should be performed in advance.

Must be recalibrated before reuse after long-term storage.

III. Regulatory and Industry Requirements?

Mandatory Verification?

According to standards like JJG 1132-2017, periodic verification is required (typically every 1 year).

Safety-critical applications (e.g., flammable/toxic gas monitoring) require calibration every 3–6 months.

Maintenance Record Analysis?

If historical calibration errors consistently increase, shorten the interval or replace the sensor.

IV. Quick Self-Check Methods?

Zero Test?

Turn off the flow and check if the reading returns to zero. If drift exceeds limits (e.g., ±0.5% FS), calibration is needed.

Standard Gas Verification?

Introduce a gas flow with a known standard rate and compare the reading to ensure it falls within acceptable error limits.

Summary:? Calibration is required when abnormal data, environmental changes, overdue verification, or regulatory mandates occur. Regular maintenance and real-time monitoring are recommended to ensure measurement reliability.