There are of two types of multimeters: analog and digital. Analog multimeters measure the electrical parameters with the help of a needle that points to the respective number, while digital multimeters display the output digitally. You can read the output numerically. This avoids the human error that may occur while taking a reading on an analog multimeter.
For measuring the resistance of a wire, first of all adjust the knob of the multimeter in the resistance range. You can see the symbol of resistance, that is ohms (Ω) on the voltmeter. There are different ranges provided for the measurement of resistance. For example, R×10, R×100 etc., are the ranges that you can set in order to measure the resistance.
Various other ranges that you will mostly find on multimeters are 1.0K, 1.1K, 1.2K, 1.3K, 1.5K, 1.6K, 1.8K, 2.0K, 2.2K, 2.4K, 2.7K, 3.0K, etc. If you are not getting any reading in a certain range, then try to select some other range and see if the scale shows a reading for that range, as your resistance wire may be in some other range.
Resistance can only be measured when the device you are testing is not powered. The multimeter may show incorrect readings if the device is powered. You can use your probe either ways, since resistance does not have any direction and so there is no question of polarities. Potentiometers are resistances and their values can be similarly measured.
For example, a normal battery source produces a direct current of 9V. Alternating current means that it changes with time. This means that the voltage changes at every instant of time. The power supply used in our homes is alternating current.
A circuit can only be tested for voltage if the power supply is on. If there is no power supply, the circuit won't work, and hence the connection is important before taking the reading. Voltage or potential drop is always measured between two points. Always place the ends of the probe between the two points, for which you wish to measure the voltage drop.
When asked to measure voltage/current, put the black colored probe (called negative, reference voltage) to the ground (it will be marked or instructed on the circuit) and put the red lead at the point where you would like to measure the current/voltage. This will give you the voltage/ampere reading.
Multimeters are handy electronic tools that are very helpful. Digital multimeters display the output in the form of numbers, as they employ decoders and encoders in the internal circuitry to represent the data digitally. Analog multimeters, on the other hand, use transducers to produce the desired output.
Transducers are the devices that convert one form of energy into another. Using a multimeter, you can check the working of a diode by knowing the current flow in the forward and reverse biased direction.