Different types of multimeters are designed with various levels of protection against the typical electrical hazards just like different types of helmets are designed to protect against labor, rock climbing or motorbike accidents. So just for your own safety you must to choose a multimeter that’s designed to protect against harmful hazards that you are most likely to face.
Things That You Must Consider
When dealing with the electrical measurements in a building you need to consider three basic characteristics. First and foremost the voltage rating which in these types of applications is known by electrical professionals is usually 230 or 477 V. Now you need to use an appropriate multimeter to measure the voltage that is expected to be present. In the second characteristic you need to consider the transient voltages when choosing a multimeter because you cannot judge everything just by considering the voltage. The transient voltages usually originate from natural causes like lightning outside the building or produced by switching operations on the power distribution system. So the multimeter should always be designed to endure these peak transients safely. The third characteristic is that you should also consider the circuit’s energy capacity. As the higher current circuits have the tendency to deliver more energy into a fault than the lower current circuits so the measurements done on higher energy circuits are way more hazardous than measurements done on the lower energy circuits. So you should always prefer a multimeter that is appropriate for the circuit’s energy capacity.
Arc flash is basically the result of a very usual mistake when using a multimeter that has some pretty serious consequences. Usually an electrician wants to do a current measurement and then want to measure the circuit voltage but he forgets the most important element to switch the test leads from the initial terminal to the voltage terminal. When the test leads tend to touch a live terminal then a high current will flow through the test leads and the meter. This fault current can turn out to be hundreds of amperes if you’re working in an area having low circuit impedance. The meter circuitry along with the test leads cannot sustain such high currents and open circuit will happen in the meter. When this happens then an arc will be made through the open part of the circuit and if it’s not immediately controlled then the arc will force the air in the vicinity to become superheated and converted to plasma. Now this is known as an arc flash and it releases a lot of energy in most of the cases.
The makers of high quality handheld multimeters have tackled the issue by introducing a special kind of high energy fuse in the meter to restrict the arc flash within the fuse before it tends to spread outside the meter. Today’s product safety standards insist on handheld multimeters with comprises of this special type of fuse on the current input circuits.
Always choose the hand held multimeter by considering the trustworthiness of manufacturer. If the manufacturer shows you a declaration of conformity only then purchase the hand-held multimeter.