Do I need calibration and how often?

This is one of the most common questions.  Firstly did you know:

• 1 in 20 high-quality new testers fail calibration.
• Safety equipment (17th edition electricians etc...) are responsible for ensuring that their testers perform.
• The criminal and financial liability is on the customer, not the supplier.
• Allowing safety testers calibrations to become out of calibration has resulted in manslaughter investigations.
• Beware it is the customers' responsibility to make sure that the calibration supplier is meeting their safety and quality needs. 
• Do not rely on a supplier being ISO 9001 because that is not a calibration accreditation.

   

If you do not calibrate equipment and there is an injury or death you could be both personally liable (don't look to the insurance) and more importantly if the HSE (or one of many other governmental bodies Police coroner....) consider you to be negligent then you could face criminal investigation such as manslaughter.  It is your risk.  

If you have ISO then you must convince them that the equipment will continue to operate within the expected boundaries.

The reason that the liability typically rests on the customer is because the calibration industry in not regulated (please see choice of supplier).

Equipment that is good quality and well treated (stored in dry conditions and not moved) would be expected to be stable for longer than equipment that is in more hostile conditions. Industry typically claims equipment would be stable for 12 months, however, we have some equipment that is calibrated every 3 months. 

If you as the customer can confidently risk that the equipment will be stable for a period of time then that is the calibration period.  If you are aware that the equipment is dropped then you would expect it to be in need of re-calibration.

For most industry and electricians 12 months would not be considered an unreasonable length of time between calibrations given the above information.
Remember you as the customer must be sure that the equipment is calibrated and meets the safety/quality needs that you require, if you are not sure of this then you would be considered negligent in the case of an incident.(please see choice of supplier).