What are the electrical measuring instruments?

“Electrical measuring instruments are widely used in teaching laboratories. This equipment is used to obtain values ​​of various quantities that are involved in an electrical circuit. With the appropriate devices we can measure electrical current, voltage and electrical resistance.

The measurement of electrical current

A device capable of indicating the presence of electric current in an electrical circuit is called a galvanometer. If it is possible to adjust the scale of this device, it will be called an ammeter, which makes it possible to measure the intensity of the electric current. There are both digital ammeters and analog ammeters, both are widely used, however the digital one allows greater precision in the results.

To measure the current in an electrical circuit, the ammeter must be connected in series with the circuit. However, this device has an electrical resistance inside, the value of which must be added to the resistance of the circuit when carrying out the calculations. In order to make the resistance of the ammeter negligible, this device is built with the lowest possible internal resistance.

The voltage measurement

The voltage measurement is better known as the potential difference measurement. To measure voltage, we use devices called voltmeters. As with the ammeter, there are also analog and digital voltmeters. Both are widely used, but the digital voltmeter allows for a better reading of the ddp value as well as certainty about what is being measured.

To measure the ddp between the ends of a resistor, for example, the voltmeter must be connected in parallel with the resistance. This device, like the ammeter, also has an internal resistance. Therefore, it is desirable that the current that diverts to the voltmeter is as small as possible, so that when the voltmeter is introduced the disturbance caused is negligible. Therefore, voltmeters are built with the highest possible internal resistance.

The measure of resistance

To measure the value of a resistance, a device called an ohmmeter is used, however, if we have a multimeter, a device that has the capacity to measure voltage values, electric current and also the resistance of the resistor, we can measure the resistance value of a resistor. To perform this measurement, simply connect the multimeter tips to the resistor terminals.”

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