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Laboratory 2: Measurement of DC Voltage and Current

20102

Laboratory #2:

Measurement of DC Voltage and Current

Objectives:

This exercise introduces the digital multimeter as an instrument for measuring DC voltage, cur-

rent, and resistance.

Pre-Lab Preparation:

1. Read Appendix A: Safety.

2. Read Appendix B: Equipment and Instrument Circuits through Digital Multimeters.

Safety Precautions:

In working with electrical equipment, extreme care must be taken to avoid electrical shock to any

person, and to avoid any damage to any instrument or other equipment. In this exercise, you are

to investigate the circuit connections for measuring DC voltages and currents. Some important

rules to remember are:

1. Always turn off power to the circuit when changing the circuit.

2. Only reapply power after verifying that the circuit is properly wired and that the voltage to be

applied is at or below the required value.

3. Failure to turn off power when making circuit changes is a major reason for blowing fuses in

the equipment, thereby rendering the equipment unusable and wasting your time and that of

others. Please carefully check circuit wiring, resistor settings, and voltage settings before ap-

plying power to the circuits.

4. To avoid possible costly instrument damage, the range of the scale for a voltmeter or an

ammeter should always be larger than the magnitude of the voltage or current being meas-

ured. When in doubt, start out with the highest scale or with an instrument known to have a

higher range than the quantity you are measuring. It is important to note that one should use

the smallest possible scale, without exceeding the range setting, for the most precise meas-

urement.

5. Polarity must be observed on DC measurements. A voltmeter must be connected such that

its positive terminal is connected to the more positive point in the circuit, and an ammeter

must be connected such that current enters its positive terminal.

6. Always connect a voltmeter in parallel with the load or source being measured, and connect

an ammeter in series with the load. Never connect an ammeter across a voltage source.

7. An ideal voltmeter would have infinite resistance and would not drain any current from the

original circuit. However, real voltmeters have a finite resistance, which must be considered

in a high-resistance circuit.

8. An ideal ammeter would have zero resistance, in which case there would be no voltage drop

across the meter. However, real ammeters have some resistance, which becomes important in

low-resistance circuits.

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BK Precision 4011A Betriebsanleitung Seite 14