In reference to users’ functional requirements, we may divide the functions of multimeter into two parts: test function and usable function.
Test function means what kinds of parameters that a multimeter can measure. The most basic multimeter can generally measure current, voltage and resistance. In addition, other common functions of a multimeter include measurements of resistance, capacitance, frequency, duty ratio, break-make, diode, temperature, square wave output, and non-contact voltage induction, etc. Users should select multimeters that have the required functions according to their own usage requirements.
Usable function refers to the peripheral functions that facilitate users to carry out testing work preferably. For example, some auto range multimeters have manual/auto switchover keys to switch the multimeters to the manual mode of range selection, thus having the merit of quick response like manual multimeters. Some multimeters have an analog strip, which is able to simulate the effect of deviation of pointer multimeters, and to help users to judge the condition of the circuit to be measured; besides, some also have the maximum/minimum value recording function, correlative value calculation function, as well as Bluetooth function and so on to help users to record measured data. Some subsidiary designs are also essential in accordance with the varied service environment of the multimeter. For instance, a user who needs a multimeter that is able to work under dark circumstances must require a multimeter with backlight; and a user who has the trouble of watching readings on the screen of multimeter may hope the multimeter has the phonetic function. Users need to determine their needs according to the service environment of the multimeter.
The use of electronic products is accompanied with dangerousness. Therefore, safety is the top priority that a user will take into account to choose a multimeter. International Electrotechnical Commission (IEC) has formulated rigid safety standards for the work under electrical system conditions. The certification authority of all countries and regions are capable of independent testing in line with the criteria designed by IEC standards. Consumers should select products with the certificate accredited by the formal certification authority. The common certifications in each region cover:
North America: FCC, UL, CUL, CSA, and ETL
Europe: CE, GS, VDE, TUV, and SGS
Asia: CNAS, CCC, PSE, KC, and PSB
Besides, misoperation often takes place when users are using multimeters. Among others, the most frequent one is to measure a voltage at an error range or at the input end, which might give rise to damage of multimeter or even harm of personal safety. Thus, it is better for users to choose a multimeter that has the function of overload protection.
3, Convenience to use
Generally, a small portable multimeter that is easy to carry is more suitable for s user who often goes out for maintenance; maintenance staff who works in fixed positions may choose more diversified and more stable medium and large multimeters or desktop ones; users who need to measure heavy current should choose a clamp multimeter; while if a user cannot spare hands to adjust function button or the driving plate as he is grasping the meter pen in two hands in the frequent maintenance, he may choose a pen-type multimeter.
4, Product stability
The product stability covers long-term stability and short-term stability. The accuracy of a multimeter is merely available under certain circumstances, i.e. ambient temperature in the range of 23℃±5℃ and relative humidity 70 percent under general conditions.
The short-term stability of multimeter covers one month and half a year, while long-term stability is one year, and five and ten years.