Fundamentals of Electrical Instrumentation

Learn how digital input devices use normally open or normally closed contacts to signal a PLC, forming a complete circuit with a 24 V DC supply and an optocoupler.

Explore sink and source input configurations by wiring a digital input to a controller, observe current flow from the power supply through the switch, and learn the waterfall memory aid.

Explore how PNP and NPN transistor input devices use three wires to switch the positive or negative leg, driving controller inputs and shaping sink or source wiring.

Wire a digital input for a controller using a 24-volt dc supply and a normally open push button, then verify the circuit closes the input.

Wire a PNP proximity sensor (inductive, normally open) to power, complete the circuit, and test with metal within 4 mm to verify a sinking input.

Explore transistors as switches and as variable devices, including use in proximity sensors and audio amplifiers, and preview digital outputs in the next chapter.

Explore how digital output devices convert controller signals into physical actions, with examples like solenoids, contactors, and indicator lights, and learn simple wiring using sourcing and sync configurations.

Wire a digital output to drive a 24 v dc solenoid valve, using a power supply and controller switch to energize the solenoid and open the normally closed valve.

Explore how to manage diverse device voltages and currents in plc systems using relays and transistor outputs, including sourcing, banked relays, and multiple voltage types.

Explore wiring digital inputs and outputs with onboard or external power supplies in sink and source configurations, and evaluate cost and load considerations for the controller's ac or dc power.

Analyze wiring diagrams to identify a 24‑volt dc system with a power supply and positive/zero rails. Note a pnp input device, sync wired inputs, and relay coils energizing the controller.

Explore how different controllers are powered and wired, with sync-wired inputs and source-wired outputs, a 24-volt supply, and testing methods using a multimeter.

We explore PLC wiring diagrams, including power supplies, digital inputs and outputs, and analog inputs and analog outputs in control systems.

Explore analog inputs and how they differ from digital ones, and how 0–10 V or 4–20 mA signals provide variable measurements for temperature, pressure, and speed to a controller.

Explore how analog inputs convert voltage or current signals to digital data via an analog to digital converter, and wire voltage and current transmitters with power considerations for PLC inputs.

Power sources vary for three-, four-, and five-wire devices when wiring to PLC analog inputs, including external 24V supplies and loop-powered two-wire transmitters; current loops reduce noise and improve accuracy.

Explore ground, differential, and single-ended wiring for analog inputs, compare their noise immunity and wiring requirements, and learn shielding, grounding, and how to connect voltage and current inputs.

Connect a 24V loop-powered 4–20 mA temperature transmitter to the controller, wiring positive to the transmitter, transmitter negative to the controller input, and use shielded control cable to reduce noise.

Explore analog output devices, their 0 to 10 volt and 4 to 20 milliamp signaling, and how controllers drive variable outputs such as a water flow valve or motor.

Learn how analog output devices translate digital control codes into analog signals using a DAC, power sources, and matching voltage or current ratings for correct terminal connections.

Explore how analog output signals carry control detail while grunt powers valves and motors via external power such as air or three-phase power.

Wire an analog current loop from the controller to the vfd's 4 to 20 milliamp input and analog common, then see motor speed rise with higher current.

Explore an installation with a controller, 24v dc supply, and digital I/O. Learn how expansion modules provide analog input and output via ribbon cables, where 'D' means analog to digital.

Configure a controller with 24-volt field power and 240-volt supply, wiring digital input and output modules, and demonstrate a PNP normally open proximity sensor driving a digital input and output.

Wires and tests an analog input and analog output, showing a 4–20 mA current loop and how the controller converts current to a voltage output.

Explore the basics of inputs and outputs in electrical instrumentation, celebrating completion of the course and encouraging continued learning in this field.