Test Equipment Safety in the Field
Are you aware of the newer safety ratings on test equipment today? If they are not listed on the tester I would think twice about buying it. Today it seems everyone is offering test equipment so how can you tell if the meter is any good?
One of the most important things to look for when buying test equipment today is to look for third-party testing laboratories certifications. A couple we’ve had around for a long time of course is UL and CE. A new one that has been around a while now that you may not have heard of is the Category rating of the test equipment. Normally where the leads go into the inputs of the test equipment you’ll find a Category rating today. The International Electrotechnical Commission or the IEC has developed a safety standards model for measurement, control and laboratory use of test equipment.
You might be surprised at the number of phone calls from customer service we get on why someone’s $20 Category II rated tester is no longer working. Then you find out someone is using it on a commercial job and the transient impulse voltages the tester experienced ruined the meter.
The higher the category rating of the test equipment the higher the peak impulse transient voltages the test equipment is designed to absorb. Keep in mind this is over a very short period of time like milliseconds not for several seconds.
Not many of us can actually sit down and figure the Peak Impulse Transient Voltage that we may experience when testing electrical circuits. So it is actually better to describe the location and environment that the test equipment is intended to be used in. If you know what the Category ratings mean you know where it is safe to actually use them and not damage either the test equipment or yourself.
Category I This is the lowest rating and the test equipment is designed for telecommunications, electronic and other low energy equipment with transient limiting protection. A good example would be inside a copy machine.
Category II The test equipment is safe to be used with loads that plug in at the receptacle outlet. Outside of walls on fixed and non-fixed powered devices including appliances, lighting and portable equipment.
All outlets at more than 10 m (30 ft) from Category III
All outlets at more than 20 m (60 ft) from Category IV
These testers are fine for the typical homeowner or hobbyist.
Category III This is the minimum rating I would recommend for electrical contractors. The test equipment can be used in electrical distribution panels and in primary feeder and branch circuits.
Permanently installed loads like motors, lighting systems, drives and load centers. Typically they are separated from the utility service by at least a single level of transformer isolation. Does not include receptacle plug-in loads, except in the case of heavy appliance outlets with “short” connections to service entrance
Category IV This is the highest safety rating and is for test equipment used at the origin of the installation (utility service) and can be used outside of building including the utility service entrance, service drop from the pole to the building, overhead line to remote buildings, underground line to a well pump and the run between the meter and the panel.
Knowing the Category rating of your test equipment will keep both you and the tester safe when working with electrical equipment.
Last edited by RonKipperDatacom; 02/08/13 03:16 PM.
