4 Types of Signals in Instrumentation

AI, AO, DI, DO

analog input

An Analog Input (AI) is like the ears of your control system. These signals come from sensors that measure real-world values such as temperature, pressure, level, or flow

analog output

An Analog Output (AO) works like the voice of the control system. Signal to control devices such as valves, dampers, or speed drives

A Digital Input (DI) is like a simple light switch. It only tells the system YES or NO, ON or OFF. These signals come from devices such as push buttons, limit switches, pressure switches, or proximity sensors

digital input

A Digital Output (DO) is like flipping a switch from the controller’s side. It sends an ON/OFF signal to start or stop a device. Typical examples include turning on a motor, sounding an alarm, or switching a relay

digital output

– Always use shielded twisted pair cables to minimize electrical noise. – Follow the 4–20 mA standard instead of 0–10 V wherever possible, as current signals are less prone to voltage drop over long distances. – Calibrate transmitters and final control elements regularly to avoid scaling errors. – Keep analog wiring separate from high voltage power lines to reduce EMI

best practices for ai, ao

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