User manual

8
2.0 Using the Digital Multimeter and Function Generator
VirtualBench includes a 5½-digit digital multimeter (DMM), which is capable of taking voltage, resistance, and current
measurements, as well as a function generator (FGEN) that can output both AC and DC signals. In this section, use both
the DMM and FGEN to explore taking power measurements of a resistive circuit.
Learning Objectives: You will understand these core concepts for VirtualBench after completing the activities in this
chapter:
1. How to generate both DC and AC signals using the FGEN
2. How to calculate DC and AC power with the DMM
3. When to take RMS measurements
2.1 Reviewing the Circuit Theory With Simulation
Follow along with these simulation experiments by using file VirtualBench Section 2_DMM and FGEN Resistor
Network.ms13.
To calculate the power drawn by a circuit, measure two of the following three characteristics: voltage, current, or
resistance. Of these three measurements, voltage is the easiest to measure since you can measure the voltage across
your power source. From Kirchhoff’s law, you know that this is equivalent to the voltage drop across your entire circuit.
Next, you can decide whether it is easier to calculate the resistance of your circuit or take a current measurement. Since
taking current measurements involves breaking the circuit into sections to measure the current flowing through each
branch, it is often easier to measure the total resistance of the circuit instead.
Now that you have decided to calculate power by taking voltage and resistance measurements, consider the circuit in
Figure 2.1.
Figure 2.1. Resistive Network Schematic in Multisim