Operational Procedure: Calibration procedures for common equipment used by the CFIA Inspectorate

Although the Safe Food for Canadians Regulations (SFCR) came into force on January 15, 2019, other requirements will be introduced in 2020 and 2021 based on food commodity, type of activity and business size. For more information, refer to the SFCR timelines.

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1.0 Purpose

The purpose of this document is to provide guidance to Canadian Food Inspection Agency (CFIA) Inspection Staff on the calibration or verification of accuracy of commonly used measurement equipment.

The guidance outlined below should be used as a reference tool to assist in ensuring that inspection equipment is accurate, operated and maintained as per manufacturer's instructions.

2.0 Authorities

3.0 Reference documents

4.0 Definitions

Unless specified below, definitions are located in either the:

Accuracy
The degree to which a measurement relates to its actual (true) value.
Calibration
is the process of correlating the readings of an instrument with those of a reference standard in order to check the instrument's accuracy.
Certified equipment
is a method of keeping records on calibrated equipment. Certification makes it possible to establish the technical level, the condition, and the working and general parameters of equipment. In the process of equipment certification, all the working parameters and control and regulatory systems are checked, and the functions of the given equipment are defined more precisely.
Certified weight
is a mass standard. Certified weights are to be certified as per manufacturer's instructions at which time the provider of this service is to issue a certificate of calibration.
Check weight
is a mass standard. Check weights are working weights used during inspection.
Gram scale
is an electronic or mechanical instrument or machine for weighing. The scales are small scales transported to inspection sites by the inspector on a regular basis as part of their inspection equipment. They are not as sensitive as a precision scale.
Precision scale
Electronic instrument used by the inspector to perform net weight verifications on finished products.
Reference thermometer
is a temperature standard. Reference thermometers are to be certified as per manufacturer's instructions at which time the provider of this service is to issue a certificate of calibration. The reference thermometer is to be at least as sensitive as the tolerance that is being used during the verification for accuracy.
Repeatability
is the closeness of agreement of readings for successive measurements of the same load test.
Standard
an object that bears a defined relationship to a unit of measure used for calibration of measuring devices.
Verification of accuracy
is the confirmation of the accuracy, correctness or effectiveness of inspection measurement tools through performance testing, visual inspection or comparison with a standard.

5.0 Acronyms

Acronyms are spelled out the first time they are used in this document and are consolidated in the Food business line acronyms list.

6.0 Operational procedure

This OG covers the following list of common equipment used by the Inspectorate which requires calibration and/or verification to ensure proper operation:

  • thermometers
  • scales and check weights
  • light meters
  • pH and chlorine test strips

For other inspection equipment that is not covered in this OG, refer to manufacturer's instructions for calibration and/or verification to ensure proper operation. Instructions must be kept readily available for the purpose of inspection or internal audits.

All tools or equipment should be used according to the manufacturer's instructions and regularly calibrated, replaced or verified as being effective. Inspection offices are encouraged to maintain a record of all equipment available to conduct inspection activities, as well as, manufacturer instructions andmaintenance/calibration logs (see Appendix 1).

A verification schedule for all applicable equipment is recommended.

6.1 Thermometers – Digital, glass, laser, infrared etc.

Note: The method below for verifying against a reference thermometer and the water bath procedure can only be used for probe type thermometers, and not for ambient thermometers.

Temperature is critical in controlling the growth and survival of pathogenic microorganisms. It is important that the inspector's thermometer is accurate. Operational and calibration instructions must be kept readily available for the purpose of inspection or internal audits.

Examples of thermometer use:

  • Egg – Verification of shelled egg wash water temperature and/or of liquid and frozen egg product temperature
  • Fish – Verification of internal temperature at receiving, on-line or final product after a cooling step
  • Plant Health – Verification of temperatures during inspection and/or re-inspection of tubers
  • All Food – Verification of product storages (coolers & freezers) or product temperature

6.1.1 Verification procedures to ensure accuracy of thermometers

When

  • All thermometers, not subject to certification, should be verified at least quarterly
  • New thermometers should also be verified before they are used, unless they are certified thermometers (also referred to as the reference thermometer)
  • When thermometers are used infrequently, meaning less than once per quarter, they can be verified for accuracy prior to use rather than quarterly
  • If a thermometer has been dropped, stored improperly or the last verification activity is unknown, it should be verified prior to use 

Tolerance

The difference between the inspector's thermometer and the reference thermometer should fall within ± 0.5°C (1.0°F).

How

There are 2 methods for verifying the accuracy of thermometers:

  1. Using a reference thermometer (this is the preferred method):
    • perform the calibration within the temperature range that the thermometer will be used
    • perform the calibration by placing the inspector's thermometer and the reference thermometer into the middle of an agitated water bath near the lower temperature limit of the temperature range
    • Let the thermometer readings stabilize and record the temperature shown on each. The difference between the 2 thermometers is used to determine if the thermometer is within tolerance.
    • Repeat in a second water bath near the upper limit of the temperature range
  2. Using the ice point and the boiling point method: Calibrate the thermometer at both points. Use this method only when a reference thermometer is not available.
    • Ice Point Method:
      • Fill a large glass with crushed ice. Add clean tap water until the glass is full and stir well.
      • Let the mixture stabilize for 4 to 5 minutes, then insert the thermometer stem or probe in the ice water mixture so that the entire sensing area is submerged. Do not let the stem of the thermometer or probe touch the sides or bottom of the glass.
      • Wait at least 2 minutes or until the reading stabilizes. The temperature on the thermometer should read 0°C ±0.5°C. Record the temperature reading.
    • Boiling Point Method:
      • Bring clean tap water to a full boil in a deep container (greater than 25 cm or 10 inches)
      • Put the thermometer stem or probe into the boiling water so that the sensing area is completely submerged. Do not let the stem or probe touch the bottom or sides of the container.
      • Wait at least 2 minutes or until the reading stabilizes. The temperature should read 100°CFootnote 1 ±0.5°C. Record the temperature reading.

Corrective Action

A thermometer outside of the tolerance should be recalibrated and rechecked to verify accuracy. If it cannot be calibrated then it should be discarded in an appropriate manner and replaced.

Records

All verification should be recorded along with the identity of the thermometer, the type of testing method, results, any corrective action required, date, name of individual performing the test and signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

  • store in a protective case
  • check before use for air bubbles, cracks or other problems that could affect accuracy
  • protect from rough handling
  • store thermometers at room temperature
  • do Not Use Mercury in glass thermometers in food production areas of a plant

6.2 Scales and check weights

Inspectors may use either a mechanical or electronic scale. All scales should be operated as per the manufacturer's instructions. Instructions must be kept readily available for the purpose of inspection or internal audits.

Examples of use

  • All Food – Verification of the declared net quantity statements on the labels of prepackaged products
  • Feed, Seed and Fertilizer– Weighing samples in the field and in sample preparation rooms

6.2.1 Verification procedures to ensure accuracy of gram scale

Prior to using the gram scale, the inspector must ensure the check weights have been verified upon receipt and on a quarterly basis thereafter (see section 6.2.3).

When

  • All scales should be verified for accuracy using a certified weight
    • immediately upon receiving and
    • at least quarterly thereafter
  • In addition, the scale should be verified using the check weight every time prior to use
  • When scales are used infrequently, meaning less than once per quarter, they can be verified for accuracy using a certified weight prior to use rather than quarterly

Tolerance

The tolerance on a scale should not exceed the manufacturer's specifications, usually ± 0.1 g for electronic scales and ± 0.25 g for mechanical scales. See manufacturer's instructions for details.

How

  • Verification is performed by weighing 2 certified weights, preferably in a range to show the scale is accurate
  • Before starting, set up the scale for reading, making sure there are no environmental conditions which may disrupt the scale (draft, vibrations or other factors which may give false readings)
  • Prior to weighing any object, make sure the scale reads zero
  • The 2 certified weights should be weighed separately on the scale and then on a verified electronic scale (the type used for net weight verifications). This should be repeated 9 times for repeatability purposes. Take measurements at one minute intervals for each set of results.
  • For electronic scales, 4 measurements from each corner of the scale's platform should be included
  • The tolerance will have to take into account the difference of the 2 scale measurements for the same weights if they are not the same

Corrective Action

Any scales operating outside of these tolerances should be adjusted according to the manufacturer's instructions (if possible) and rechecked to verify accuracy. If the scale is still inaccurate, it should be sent out for repairs or discarded.

A correction factor may be used to finish an inspection, however the scale should be sent out for repair at the completion of the inspection.

Records

All verification should be recorded along with the identity of the scale, the type of testing method, results, any corrective action required, date, name of individual performing the test and signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

  • Protect from rough handling
  • Store the scales at room temperature away from high humidity conditions is recommended
  • Store the scales in such a manner that the weighing pan is not under a load

6.2.2 Verification procedures to ensure accuracy of precision scale

Prior to using the precision scale the inspector must ensure the check weights have been verified for accuracy within the past year (see section 6.2.4).

When

  • The precision scale is highly stable and requires detailed scale performance tests quarterly
  • It is recommended the regular scale check be completed prior to use at each inspection location
  • When scales are used infrequently, meaning less than once per quarter, the detailed scale performance test can be completed prior to use rather than quarterly

Tolerance

For the precision scale used for net quantity verification and having a readability of 0.1 grams, adjust the tolerance figure upwards (for example 54.26 g adjusted to 54.3 g).

How

Regular scale check, this should be completed before each inspection and should include the following procedures:

  • conduct a full-scale or specific weight calibration
  • conduct a platform shift test
  • check for zero drift

Detailed scale performance tests (quarterly), this full calibration of the scale must take place before the following are done:

  • check for zero drift
  • conduct a platform shift test
  • conduct an ambient calibration
  • conduct a linearity test

Detailed instructions can be found at: Precision Scale - (internal access only)

Corrective Action

Any scales operating outside of these tolerances should be re-calibrated according to the manufacturer's instructions (if possible) and rechecked to verify accuracy. If the scale is still inaccurate, it must be sent out for repairs or discarded.

Records

The verification and results should be recorded along with the identity of the scale, any corrective action required, date, name of individual performing the test and signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

Detailed instructions on the proper care, use and shipping of electronic scales must be followed by all inspectors and can be found at: Precision Scale - (internal access only)

6.2.3 Verification procedures to ensure accuracy of check weight for gram scale

The check weights are used to verify that the scale is operating as designed and will support the inspector's observations.

When

  • All check weights for scales should be verified for accuracy upon receipt and on a quarterly basis thereafter
  • If the check weights are used infrequently, meaning less than once per quarter, they can be verified prior to use

Tolerance

The tolerance for check weights should not exceed ± 0.1 g as compared against a certified weight using a scale of the type used to perform net weight verifications.

How

Verification will be performed by comparing the weight of a check weight against that of an equivalent certified weight. The difference is used to determine if the check weight falls within tolerance.

Corrective Action

  • When check weights are first received from the manufacturer, they should be checked to ensure they fall within the tolerance
  • Check weights that do not fall within the tolerance should be returned to the supplier, as calibration of such an item is not practical
  • Thereafter, check weights which do not fall within tolerance should be discarded to prevent further use and replaced with ones that fall within tolerance

Records

All verification should be recorded along with the identity of the check weights, the type of testing method, results, any corrective action required, date, name of individual performing the test and his or her signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

As per manufacturer's instructions

6.2.4 Verification procedures to ensure accuracy of check weight for precision scale

The check weights are used to verify that the scale is operating as designed and will support the inspector's findings. Prior to using the precision scale the inspector must ensure the check weights have been verified for accuracy within the past year.

When

Check weights used with the precision scale are to be verified for accuracy on an annual basis against a certified weight to which a certificate of calibration has been issued.

Tolerance

The tolerance for check weights should not exceed ± 0.1 g as compared against a certified weight using a scale of the type used to perform net weight verifications (such as precision scale).

How

As per manufacturer's instructions

Corrective Action

As per manufacturer's instructions

Records

The verification and results should be recorded along with the identity of the check weights, any corrective action required, date, name of individual performing the test and his or her signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

As per manufacturer's instructions

6.3 Light meters

There are a number of different light meters used by the Inspectorate. It is the inspector's responsibility to ensure that the light meter is working properly and is operated as per manufacturer's instructions. Before using a light meter the inspector must review the most recent certificate of calibration to ensure it has been calibrated within the time frame of the manufacturer's recommendation. 

Examples of use: 

  • During an evaluation of a CFIA licenced operator's compliance to the requirements for a preventive control plan (PCP) by conducting a PCP inspection following the Standard inspection procedure (SIP), if the inspector suspects the lighting is inadequate, a light meter could be used to evaluate the lighting intensity under sub-element 5.2.

6.3.1 Verification procedures to ensure accuracy of light meters

When

As per manufacturer's instructions

Tolerance

As per manufacturer's instructions

How

As per manufacturer's instructions

Corrective Action

As per manufacturer's instructions

Records

The verification and results should be recorded along with the identity of the light meter, any corrective action required, date, name of individual performing the test and his or her signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

As per manufacturer's instructions

6.4 pH paper, chlorine & other test strips

Chemical and pH concentrations are important in controlling the growth of microorganisms.  In order to obtain accurate readings from test strips, inspectors should follow instructions regarding usage, storage, and where applicable, the expiry date.  When an expiry date exists and is only on the master container of test strips the inspector must transfer that information to individual containers.  Ensure they are stored properly and discarded after the expiry date.

Examples of use:

  • Egg – Verification of pH of the wash water used in egg basket washers and recirculating washers
  • Sprouted seeds – Verification of chlorine concentration of antimicrobial treatment for sprouted seeds
  • Fresh Fruits and Vegetables – Verification of pH and chlorine concentration of wash water used in minimally processed ready-to-eat vegetables
  • Sanitation, Foot dip or Hand dip stations – Verification of sanitizer strength.

6.4.1 Verification procedures to ensure accuracy of test strips

When

As per manufacturer's instructions

Tolerance

As per manufacturer's instructions

How

As per manufacturer's instructions

Corrective Action

As per manufacturer's instructions

Records

The verification and results should be recorded along with the identity of the light meter, any corrective action required, date, name of individual performing the test and his or her signature. These records should be maintained on file and be made available upon request. See Appendix 1 for template.

Storage and Handling

As per manufacturer's instructions

6.5 Certified equipment

For all equipment requiring certification including, but not limited to, certified weights, light meters and reference thermometers, a record of certification by the manufacturer or calibration service provider should be available. Inspectors should verify that the equipment has been certified annually or at the recommended frequency.

7.0 Appendix

For general inquiries related to this operational guidance document, please follow established communication channels, including submitting an electronic Request for Action Form (e-RAF).

7.1 Appendix 1: Equipment calibration and/or verification of accuracy log

Equipment Name Equipment Identification Number
(if applicable)
Tools Used for Calibration /
Verification of Accuracy and Identification (if applicable)
Program Region / District
Date
(yyyy/mm/dd)
Verification Test Method Test Results Corrective Action Comment Name of Person performing test Signature

Verified by (name and signature)
Date

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