 ### 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. 7.74K
×
Measuring DC Current

#### Project 2: Digital Multimeter

Introduces the use of digital multimeters for current measurement. 7.71K
×
Measuring Resistance

#### Project 3: Digital Multimeter

Introduces the use of a digital multimeter for resistance measurement. 12.5K
×

# Measuring Resistance

## Introduction

This experiment introduces the use of a digital multimeter for resistance measurement. It is also designed to increase understanding of resistance. Resistance is theopposition to current flow between two points. This value has only magnitude, there is no direction or polarity associated with resistance—it is always a positive value.

Although resistors are created with color bands that indicate their values, the total resistance of an object can be more accurately measured with an Ohmmeter. In this experiment, we will use a Digital Multimeter (DMM) as an Ohmmeter to measure the resistance of resistors. We will also examine a few ways that measurements can be done improperly to produce incorrect results.

##### Before you begin, you should:
• Be able to identify fixed resistors by their color bands.
##### After you're done, you should:
• Be able to use a digital multimeter to measure resistance.

## Inventory:

Qty Description Typical Image Schematic Symbol Breadboard Image
1 Digital multimeter (DMM)   1 Any resistor   1 A different resistor   2 Analog Discovery™ pins  ## Procedures

### Step 1: Measure the Resistance of an Individual Resistor

#### A. Create the circuit

1. Place the two resistors on the breadboard so that none of their terminals are connected to one another.

2. Once on the breadboard, place the mode selector on your DMM to the Ω symbol. Ensure that your leads are plugged into the V-Ω and COM ports.

3. Place one probe on each side of a resistor to obtain its resistance value.

#### B. Measure Resistances

1. Measure and record the individual resistance values of the resistors.

2. Use the color codes on the resistors to determine an expected resistance value. Does the expected value agree with the measured value?

### Step 2: Measure Resistance of a Resistor in a Circuit

#### A. Create the circuit

1. Connect the resistors to one another as shown.

2. Connect the AWG lead (W1), to the first resistor.

3. Connect the second resistor to the ground ( ) terminal.

4. Do NOT turn on the AWG!

#### B. Re-measure Resistances

1. Re-measure the individual resistance values of the resistors.

2. The values you have now should be different than those you first measured. What caused the resistance measurement to change?
• Because these resistors are now in a circuit, the Ohmmeter measures how much resistance there is to current flow through EVERY available path. This includes the path through the Analog Discovery and the other resistor.
3. The moral of this experiment: always remove components from circuits before measuring their resistance values.