Just because a test tool is designed to meet the safety standards for test and measurement equipment doesn’t guarantee that the tool actually meets those safety requirements. Only trust test tools that have been independently tested and proven to meet the standards.
It may sound logical that, as long as you choose a multimeter with a high enough voltage rating for the measurement you’re about to take, your safety should be assured. But we all know this isn’t so. Besides the accidents that happen when someone subjects a meter to a higher voltage than what it’s rated for, there is also the possibility of high-voltage spikes or transients being present, whether from internal fluctuations based on the operation of other components or from external lightning strikes.
Two of the standards that are most often used in the test and measurement world include the International Electrotechnical Commission (IEC) standards and Conformite Europeenne (CE) standards. Compliance to either of these standards is no doubt important when you go to buy your product. In fact, IEC goes so far as to create specific measurement categories from Cat. I for protected equipment like computers and other electronics to Cat. IV for three-phase utility connections close to the primary overcurrent protection equipment. Even these specifications can be misunderstood if the user doesn’t read up on transient test values for each category. For example, a Cat. II meter may be rated at a working voltage of 1,000 V but can only handle a peak impulse transient of 6,000 V, whereas a Cat. IV meter rated at a working voltage of only 600 V can actually handle a peak impulse transient of 8,000 V.
