• About ECS
• What is calibration?
• What calibration isn’t
• Traceability
• Sound/Noise Monitoring Equipment Calibration
• Sound Level Calibrator
• Audiometric Equipment Calibration
• Calibration Intervals
• Advantages of Calibration
• Some practical points

About ECS

ECS is a limited liability company specialising in the calibration and servicing of acoustical test and measurement equipment. It is a registered Laboratory in the field of metrology and calibration conforming and complying with ISO Guide 25 and ISO 9002 for laboratories since 1981. ECS is also accredited to ISO 17025.

The staff of ECS has between them over 38 years of experience in this specialist field. We have a well maintained and fully equipped laboratory catering for all our customers needs.

Quality is an ongoing commitment, to that end we participate in International proficiency testing programs. We provide prompt turn-around calibration for pre-scheduled equipment.

What is calibration?

• Calibration is the comparing of a measurement device (an unknown) against an equal or better standard.
• This standard is considered the reference.

What calibration isn’t

• It is not an unsubstantiated claim of competence and traceability by an agency saying "trust us we know what we're doing".
• It is not an organisation that has not undergone any form of independent external audit.
• It is not achieved through a list of serial numbers claiming that instrument #123 was calibrated against instrument #456 which was calibrated against instrument #789. There is no assurance any instrument calibration was performed in a competent manner.
• It is not achieved by believing the unsubstantiated claims of accurate traceable calibration made by instrument manufacturers and/or agents who have no independent, external certification or accreditation.
• It is not achieved by relying on a reference instrument that does not have a current calibration.

Traceability

• Traceability is an unbroken chain of comparisons from the measurement being made to a recognised national legal standard.
  
• Making a measurement is only part of the calibration process. All data concerning the test units response is recorded. This information supports the traceability of the test.

Sound/Noise Monitoring Equipment Calibration

• The success of any noise measurement depends on routine calibration of the measurement instrument, whether it be type 1 or type 2, particularly when the results may be used for legal purposes.
  
• A valid calibration of an acoustic instrument requires that the entire instrument from the microphone to the indicating meter be checked.
  
• In a laboratory calibration the microphone and indicating meter are tested against international standards. For example the sound level meter would have such things as the weighting networks, level linearity, time-weighting and RMS response tested. The field sound calibrator cannot test these features.

^^top

Sound Level Calibrator

• The portable sound level calibrator, which should be used before and after noise measurements is a field calibrator. It generates a precise known stable acoustic level at the microphone with the level high enough so that readings are unaffected by normal background noise. This provides only a simple functional check of the sound level meter.
  
• A sound field calibrator should not be confused with a full instrument calibration where the complete set is sent to an organisation which can provide calibration to International standards and has demonstrated a high level of competence recognised by an authority such as IANZ (previously Telarc).

Audiometric Equipment Calibration

• To ensure your equipment complies with current standards and fulfils your company obligations (for ISO9000 registered companies) it will need calibrating by an independently audited laboratory; such as ECS Ltd.
  
• As companies become aware of their obligations to minimise noise in the work place and to protect themselves against Accident Compensation Corporation (ACC) claims for loss of hearing, it is the occupational health services that are front line investigators, to comply legal requirements it will be necessary to provide evidence that equipment used is calibrated.
  
• As part of ECS’s procedure, parts that influence your results are inspected and deteriorated items replaced as required. This includes such things as earpads and damaged headphone cables.)

^^top

Calibration Intervals

Acoustic equipment:

Typically manufacturers of sound level meters give a calibration interval of one year. Our records show that this type of equipment is generally stable in operation and apart from obvious faults does not require such a short interval. We have always recommended a two year interval as being adequate. However, if an instrument has a one year period on its sticker this does not mean that you can add on a further year. The instrument will be outside calibration once the stated period has expired.

It is recommended that field sound calibrators and measurement microphones used on sound level meters be calibrated annually. These are sensitive devices and in the case of the microphone can be positioned in hostile environments. We do not expect users to routinely remove microphones and send them in for calibration and provision has been made in the appropriate NZ standards on environmental noise to allow for a biennial calibration along with the sound level meter.

Audiometric equipment:

Clinical audiometers are generally used at a single location and can be a significant cost both aspects lend to users taking more care with the equipment. The overall result means a 2 year calibration interval is adequate.

Screening audiometers, tympanometer and impedance instruments have a recommended 1 year recalibration interval.

Advantages of Calibration

Established stability history

• enables early detection of possible deterioration
• allows for preventative maintenance for minimum down-time

Provide confidence in measurement results

• traceable to International Standards

Fulfil company quality guidelines

• necessary for compliance with ISO9000

Some practical points

Using a calibrated instrument does not imply that the instrument complied with the standard it was tested against. From the definition of calibration we know that calibration is a comparison. So, a calibration sticker lets us know the instrument has been tested. It says nothing about the status of the equipment other than the fact it was working when tested. The user must refer to their calibration report to find any non-compliance issues noted during testing.

A certificate of conformance is not a calibration certificate. Instead it is a document issued from a manufacturer stating an instrument complies with manufacturer specifications usually based on checking procedures in the service manual. It does not provide a traceable test path.

Users should insist that new equipment comes with a traceable calibration. This is for obvious reasons. But primarily for satisfaction that it is operating in accordance with the standard that it was designed to meet. We sometimes see new equipment that does not comply with the specified standards, but if it has not been independently calibrated from new, the warrantee period has likely expired leaving you with substandard equipment or costly repairs.

^^top