In this lesson, the instructor discusses the difference between testers and meters in the context of electrical work. A meter is fixed to a panel and is used to measure volts or current on that panel. A tester, on the other hand, is a handheld device used to test for voltage, current, and resistance. The instructor demonstrates the use of a multimeter, which can measure various parameters such as volts, amps, ohms, capacitance, and temperature. They explain how to select the correct settings and scales on the multimeter for different measurements.

For voltage testing, the instructor shows how to connect the multimeter in parallel to measure the potential difference between two points in a circuit. They emphasize the importance of ensuring the correct placement of the leads and selecting the appropriate voltage scale on the meter.

To measure current, the instructor explains that the multimeter needs to be connected in series within the circuit to measure the flow of electrons. They highlight the difference in resistance between a voltmeter and an ammeter, and the need for a low resistance in the ammeter to avoid voltage drops.

The lesson also covers the use of a clamp tester or tong tester, which measures the magnetic field around a conductor to determine the current. The instructor mentions that the tong tester may not be as accurate as a multimeter but can still provide a good indication of the current.

Additionally, the instructor discusses the testing of resistance using the multimeter and advises that the power should be switched off before measuring resistance across a component. They demonstrate the proper placement of leads and scale selection for resistance measurement.

Finally, the instructor conducts a live demonstration at an electrical panel, replicating the circuit discussed earlier. They measure voltage, current, and resistance using the multimeter, tong tester, and line tester, highlighting the readings obtained and their significance.

Overall, the lesson provides an overview of testers and meters, their functions, and the proper techniques for using them in electrical testing and measurement.