 ### Intermediate Analog Discovery, Module 2

• Measuring DC Voltage

#### Project 1: Digital Multi...

Introduces the use of digital multimeters for voltage measurement.

• Measuring DC Current

#### Project 2: Digital Multi...

Introduces the use of digital multimeters for current measurement.

• Measuring Resistance

#### Project 3: Digital Multi...

Introduces the use of a digital multimeter for resistance measurement.

Measuring DC Voltage

#### Project 1: Digital Multimeter

Introduces the use of digital multimeters for voltage measurement. 11.5K
×
Measuring DC Current

#### Project 2: Digital Multimeter

Introduces the use of digital multimeters for current measurement. 10.1K
×
Measuring Resistance

#### Project 3: Digital Multimeter

Introduces the use of a digital multimeter for resistance measurement. 21.4K
×

# Measuring DC Voltage

## Introduction

This experiment introduces the use of digital multimeters for voltage measurement. Digital multimeters, or DMMs, perform a variety of functions. When measuring voltage, the DMM is operating as a voltmeter. More information relative to DMMs and their use in voltage measurements are provided in the links to the right.

Voltages in a circuit are a difference in electrical potential energy between two different points in the circuit. DMMs generally have two terminals, or leads. When the DMM is operating as a voltmeter and its leads are connected to two different points in a circuit, the DMM will display the voltage difference between the two points.

##### Before you begin, you should:
• Be able to use the voltage instrument on the Analog Discovery™ to apply ±5V relative to the Analog Discovery's ground.
• Be able to use the Analog Discovery voltmeter to measure constant voltages.
• Be able to state how the reference voltage polarity and connection of voltmeter terminals are related to the sign of the measured voltage.
##### After you're done, you should:
• Be able to use a digital multimeter to measure constant voltage.

## Inventory:

Qty Description Typical Image Schematic Symbol Breadboard Image
1 LED   2 100Ω resistor   1 Digital multimeter   ## Procedures

### Shortcut!

• Parts A and B of this project are also done in the Voltmeter Instrument project. If you've already completed that project and your circuit is still intact, simply disconnect the Analog Discovery voltmeter connections, add the DMM connections (as shown in Parts B and C of Step 1 in this exercise), and read the voltage difference using the DMM.

### Step 1: Understanding the Circuit

#### A. Circuit Schematic

1. Use V+ to apply 5V across the LED to light it up.

2. The resistor limits the current.

3. To measure the voltage V, connect the V-Ω terminal of your DMM to the diode's anode and the COM terminal to the diode's cathode.

#### B. Create Basic Circuit

1. Connect V+ (red wire) to the 100Ω resistor.

2. Connect the 100Ω resistor to the LED anode.

3. Connect ground ( , the black wire) to the cathode of the LED.

#### C. DMM Setup and Connections

1. Connect the V-Ω terminal of the DMM to the diode's anode.

2. Connect the COM terminal of the DMM to the diode's cathode.

3. Turn the function selection knob on the front of the DMM to the position.

### Step 2: Set up Instruments

#### A. Open Voltage Instrument

1. Open WaveForms™ to view the main window.

2. Click on the Voltage instrument icon to open the Power Supplies window.

#### B. Turn on Power and Determine Diode Voltage The above screenshots are of Digilent WaveForms running on Microsoft Windows 7.

• The LED should light up and the DMM should display the voltage difference across the diode.