Explain the construction and working of series type
ohmmeter with a circuit diagram.
Answers
What is an Ohmmeter?
An ohmmeter (also known as an ohm meter) is an instrument that measures the electrical resistance of a material (resistance is a measure of the opposition to the flow of electric current). Micro-ohmmeters (micro ohmmeter or microhmmeter) and Milliohmmeters make low resistance measurements, while Megohmmeters (a trademarked device by Megger) measure large values of resistance.
Every device has electrical resistance. It may be large or small, and it increases with temperature for conductors and decreases with temperature for semiconductors.
There are many types of ohmmeters. Three of the most common ohm meters are:
1.Series ohmmeter.
2.Shunt ohmmeter.
3.Multi-range ohmmeter.
Working Principle of Ohmmeter
The instrument is connected with a battery, a series adjustable resistor, and an instrument that gives the reading. The resistance to be measured is connected at terminal ob. When the circuit is completed by connecting output resistance, the circuit current flows and so the deflection is measured.
When the resistance to be measured is very high then the current in the circuit will be very small and the reading of that instrument is assumed to be the maximum resistance to be measured.
When resistance to be measured is zero then the instrument reading is set to zero position which gives zero resistance.
