When on certain occasions we need to measure the intensity, voltage and resistance in a circuit, we use an instrument that allows us to carry out this multifunction and measure the three quantities at the same time: the multimeter. There are two types of polymeters, analog, which give us the reading by means of a needle on a graduated background; and digital ones whose handling is much easier and also have a cheaper price.
PARTS OF A POLYMETER
The main elements of all polymeters are:
-A galvanometer: an instrument that is used to measure and detect electric current, which is used to measure each of the magnitudes of electricity.
-A switch: that allows us to change the different functions that we want to perform.
-Electric pumps: used to connect the multimeter to the circuits or devices that we want to measure. They are usually two or more, one red and one black; the red one is for the one with the highest potential and the black one for the one with the lowest potential when working with direct current.
-An internal battery: that allows us to measure passive magnitudes.
In addition, digital multimeters also have the following elements (which are mainly reflected in their appearance):
-The screen: it is the same as the screen of calculators, it is made of liquid quartz and we can read different measurements.
-The function selector: a rotating roulette wheel that is in the center occupying the large part of the multimeter as we can see in the previous image; which we have to turn to select the type of measurement we want to do.
The circuit diagram of a multimeter is as follows: MEASURING RESISTANCE When we want to measure the resistance of electricity with our multimeter we have to follow the following steps:
1st. We plug the black plug to the part where it puts the initials COM and the red one where it is marked with VΩ, as we can see in the image. 2nd. We place the roulette in the zone corresponding to the zone to carry out the resistance measurements. 3rd. We play with the pointers on the part of the circuit that we have isolated.
MEASURING THE VOLTAGE
Before starting, we must bear in mind that current must pass through our circuit. Then we carry out the following steps, making sure of the type of current we want to measure, direct or alternating.
1st. Plug the pointers the same as in the previous position.
2nd. Place the roulette in the position to measure tension.
3rd. Place the pointers on the corresponding part of the circuit.
MEASURING THE INTENSITY
To measure the intensity, we proceed analogously to the previous cases, with the difference that in this case we will mount the circuit in series, that is, the circuit and the multimeter must be connected in parallel. Then we will follow the next steps after once again making sure of the type of current we want to measure.
1st. We place the black pointer on the COM plug, while the red pointer we put on the mA plug.
2nd. Put the roulette in the right place.
3rd. Put the pointers at the two ends of the circuit that we have left free in such a way that the current circulates inside the multimeter.
