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Name Professor Course Date VOLTMETER LOADING EFFECT – LAB REPORT Objective: To determine the loading effect of a voltmeter to a circuit Prerequisite Knowledge: Electric circuit principles Required Equipment: 2kΩ, 20kΩ, and 200 kΩ resistors. DC power supply (0-12V) VOM (DC sensitivity 20 kΩ/V) DMM (>10 MΩ input impedance). Theory: Making measurements in electrical circuits, and generally in science without affecting the result of the measurement is not very easy. This phenomenon is known as loading in electronics. In measuring current, for instance, the resistance of the ammeter contributes to the final reading shown, hence a lower value as shown by the deflection of the ammeter. In a voltmeter on the other hand, the contribution leads to parallel resistance, leading to lower voltmeter reading. The extent to which the loading effect affects the voltmeter reading is determined by the magnitude of the resistance of the device. It is necessary to connect a voltmeter in parallel so that it doesn’t affect the circuit. All the meters used in circuits have little resistance. The VOM which is meant for use in this experiment has a resistance of upto 20 kΩ/V. A good DMM has a resistance of up to 10 MΩ. DMM gives the best reading. This experiment is used to demonstrate the loading effect of a voltmeter. A 2-resistor circuit is used together with both VOM and DMM to measure voltage. Procedure:The equipment is arranged as shown above. The voltages V1 and V2 are calculated and recorded. The most suitable range for measuring the voltages is decided by inspecting the VOM. The VOM sensitivity figure can be used to ascertain this and then the meter
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