A multimeter is a portable electrical device used to directly measure variouselectrical quantities, these can be active as currents, voltages orpotentials, and also passive quantities such as resistors and capacities.
There are mainly two types of multimeters, analog and digital. Generallyboth types should be able to measure the three most common quantities: volts,amps, and ohms.
A digital multimeter is an indispensable tool for all work involving electricity,so it is very important to make the right choice. For choosing adigital multimeter it is important to take several considerations, such as:
- The working environment, this includes thinking about the voltage level withwhich to work, and types of measurements to be made.
- The extra featuresor functions with which we want to count (frequency, temperature,non-contact voltage, min-max register , etc.), these additions arevery helpful on many occasions and reduce the amount of differenttools or equipment that we must buy.
- Accuracy and resolution. This is one of the most important aspects and one thatlargely defines the quality of the multimeter.
- Safety, test equipment must be designed to protect people working in high voltage andhigh current environments. Multimeters must meet certain safety standards,depending on the work environment where they will be used.
In a more technical way, the main parameters to which we must pay attentionare the following:
Resolution can be understood as sensitivity in measurement. The resolution of adigital multimeter is expressed by the number of digits it can display on thescreen. A 3 ½ digit multimeter means it has 3 integer digits from 0 to 9and one that can change between 0 and 1, so the resolution would be ± 1,999. Mostmultimeters on the market have 3 ½ or 4 ½ digits with a range of ± 1,999or ± 19,999. Some manufacturers specify the resolution as " count "or counts. This count is the largest number you can measurebefore you need to change range. A 4 ½ digit multimeter can be specifiedas 19,999 or 20,000 counts.
The precision of a multimeter is the maximum error allowed in the readings. Thisis normally expressed as ± (% error in reading + least significant digit orLSD). The LSD represents the error caused by the circuitry, such as noiseand tolerances of the ADC converter.
On a 4 ½ digit multimeter with a DC voltage accuracy ± 0.05% + 3. While measuring12V VDC, the multimeter will be able to display something between 11,994 and12,006 V. But when you take the LSD into account the last digit can varybetween ± 3, then you can have readings between 11,991 V to 12,009 V.
Apart from these general characteristics, the equipment oriented to morespecific work areas have others such as IP68 certification, magnetic holder,removable screen, among others.
A very good multimeter that you can buy with a excellente price quality ratio is the MESTEK DM100C, I bought this multimeter and I am very satisfied with it.
Have a excellent quality of construction and a lot of functions like Non Contact Detection Voltage (NCV), Lantern, True RMS, Manual range and automatic range, V.F.C variable frequency voltage measurement function, measurement of temperature, among other.
For some people, the instant it takes to select the range automatically can be a bit annoying. There is also a version without the function of said automatic range for a lower cost.