Scales are important pieces of equipment in industries ranging from manufacturing and pharmaceuticals to food production and logistics. Accurate measurements ensure product quality, regulatory compliance, and operational efficiency. However, a scale’s accuracy can drift over time due to wear and tear, environmental factors, and usage frequency. This raises the question: how often should you calibrate your scale?

How Often Should I Calibrate My Scale?

This is one of the most common questions we get asked at Scales Plus. The answer isn't one-size-fits-all. At a minimum, we generally recommend calibrating scales at least once per year. However, there are a variety of considerations to make, and reasons why a scale should be calibrated more often. Beyond a regular calibration schedule, there are factors that would prompt a verification and calibration outside of regularly scheduled checks.

Factors Influencing Calibration Frequency

Type of Scale

The sensitivity and precision of a scale impacts its calibration needs. Analytical balances, which measure with high precision, require more frequent calibration compared to standard industrial scales. Because balance scales are higher precision, the load cells and electronics have tighter physical tolerances, which means there is a larger impact on performance from smaller external influences like shock, temperature fluctuations and vibrations.

Manufacturer Recommendations

Scale manufacturers often provide guidance on calibration frequency. These recommendations consider the scale’s design, intended use and performance specifications. Of course, this is just a baseline recommendation, so you'll want to consider other factors beyond the manufacturer's recommendation.

Usage Frequency

Scales used daily or continuously are more prone to wear and may require more frequent calibration. For example, a scale in a busy shipping department should be checked more often than one used occasionally in a laboratory. For scales that run on production lines 24/7, the frequency they are calibrated should be more often. It is common to schedule weekly, or even daily, calibrations for high-throughput environments.

Environmental Conditions

Temperature fluctuations, humidity, vibrations, and exposure to dust or chemicals can affect a scale’s accuracy. For instance, a scale in a humid or dusty warehouse may need calibration more often than one in a climate-controlled laboratory. If dust or other debris are factors, be sure to use a scale rated for harsh environments, and clean them well before performing a calibration.

Regulatory Requirements

Many industries are governed by standards that dictate calibration intervals. For example, pharmaceutical companies must comply with Good Manufacturing Practices (GMP), which include guidelines for equipment calibration schedules.

Client Quality Requirements

For contract manufacturing, packaging and other contracted services, clients may require specific quality control guidelines that dictate the performance of their suppliers. This often times includes conformity to the same regulations that dictate their processes, which may include quality checks related to tooling and equipment. 

Critical Applications

For critical applications, which may include medical or pharmaceutical applications, frequent calibration ensures reliable measurements, reducing risks to safety and compliance. Research and development applications where accuracy is paramount would also be subject to more frequent calibrations.

Historical Performance

Regularly reviewing a scale’s calibration history can help identify trends. If a scale frequently drifts out of tolerance, it may need more frequent checks. Fine-tuning calibration schedules is an on-going practice.

Establishing a Calibration Schedule

To determine an appropriate calibration frequency, and also ensure timely calibrations, it is important to establish a calibration schedule. The following is a list of important details you need to review to come up with an appropriate calibration interval for your equipment.

Risk Assessment

Evaluate the potential impact of inaccurate measurements on your operations, safety, and compliance. High-risk environments warrant more frequent calibration. Risk assessment may also directly relate to client quality requirements.

Consult Industry Standards

Refer to standards like ISO 9001, ISO/IEC 17025, or industry-specific guidelines to establish baseline calibration intervals.

Set Usage-Based Intervals

For scales in heavy use, consider daily or weekly calibration checks. For less frequently used scales, monthly or quarterly intervals may suffice.

Maintenance Calibrations

There are times your scales may need to be calibrated outside of their normal schedule. A variety of circumstances can necessitate a verification, and potential re-calibration. These may include environmental changes, physical disturbances and equipment failure. 

If any of the following occur, be sure to verify accuracy, and if needed, perform an out-of-schedule calibration.

Physical Impact

If a scale is dropped, overloaded, or jarred in any significant way, it should be removed from operation and checked immediately. Physical impacts are one of the most common reasons scales lose their calibration.

Environmental Change

Changes in humidity or temperature can alter the performance of a scale. For example, relocating a scale from a climate-controlled area to a non-climate controlled area may influence the load cell and its performance. This is why it is often recommended to re-calibrate a scale whenever it is moved from one location to another.

Overloading

Overloading a scale occurs when the rated capacity is exceeded. When this happens, it may cause a change to occur in the structure of the load cell, therefore changing the scales performance. Most scales have overload protection to a degree, but it is still recommended to verify for accuracy, and if necessary, re-calibrate the scale.