What Is the Difference Between a Schematic & a Wiring Diagram?

Electronic devices and systems have schematics and wiring diagrams to assist in building them and troubleshooting problems. The differences between the two are minor yet important.

Every electrical component, such as a resistor, capacitor and inductor, has a standard symbol used to represent it in a circuit. Each component comes in a variety of packages, which differ in size, shape and sometimes color. Think of the circuit symbol as a toy and the package as the box the toy comes in.

Schematics are symbolic representations of complete circuits or systems created during the design phase. They show the function of the circuit or system. The schematics reduce multipart components, or integrated circuits, into their sub-components so their role in the circuit is easier to understand.

Wiring diagrams, or layouts, illustrate the physical connections, or wiring, between components. They are crucial to the assembly of the circuit or system. Parts that are shown broken down into their sub-components, for the schematic, retain their complete package format for the wiring diagram.

To read a schematic, you need to understand the symbols for various electronic components. It's also helpful to know how to analyze the circuits to determine their function.

Schematics often assign labels to parts based on their type and arbitrary ordering on the schematic. For example, R stands for resistor; on a schematic with numerous resistors, it might show the first resistor on the left-hand side of the schematic labeled as R1.

To read a wiring diagram, you need to understand the types of packages available for different parts. For large-scale wiring diagrams, such as those for a house, how-to books and other resources on installing electrical components provide symbols. For wiring diagrams for a small circuit, such as the one found in a cell phone, a parts list provides the information needed to look up each component’s packaging on its manufacturer’s website. In some cases, the schematic symbol and the wiring diagram symbol are the same. Many wiring diagrams also have a key that provides important information such as wire gauge and colors.

Wiring diagrams for circuits use the same labels as the schematic. Using the same example as above, the wiring diagram includes R1 from the schematic but, instead of being on the far left, it is depicted in the middle, which is its actual location on the circuit board.