latency

In industrial electronics, latency is the time gap between when a signal is sent or a command is issued and when the system actually responds or executes that command. For a machine tool receiving a positioning instruction, latency might be 5 to 50 milliseconds. For a safety interlock monitoring a press, it might be 10 to 200 milliseconds. For analog-to-digital conversion in process control, it can be as little as microseconds. The source of latency is rarely obvious; it lives inside software queues, communication protocols, processor cycles, sensor response times, and actuator inertia, often all at once.

Latency matters because many industrial processes are time-sensitive. A conveyor belt sorting system checking 60 packages per minute cannot afford 500 ms of delay; the part will already be gone. Motor speed control, pressure regulation, and flame detection in combustion systems all demand latency within their operating envelope or the process fails to perform as designed. The tighter the control loop, the more critical latency becomes. This is why real-time systems in manufacturing specify maximum latency in their technical requirements, not just average response time.

Sources and Trade-offs

Latency accumulates at every stage. A networked PLC might add 10 ms from transmission protocol overhead. The sensor itself might introduce 5 ms. The processor may need 2 ms to evaluate the input against setpoints. The output driver adds another 1 ms before the relay or solenoid actually moves. Each layer is small; the total often surprises engineers. Wireless industrial systems routinely exhibit 50 to 100 ms latency, making them unsuitable for closed-loop control but acceptable for supervisory monitoring.

Reducing latency costs money and design effort. Hardwired analog control loops have almost no latency; networked digital systems do. Local processing is faster than cloud-based processing. Deterministic real-time operating systems guarantee maximum latency; general-purpose systems do not. Many equipment designers accept latency as a fixed constraint and build their control algorithms around it, rather than trying to eliminate it.

The term latency is borrowed from telecommunications and computing, where it originally meant propagation delay down a cable or across a network. In industrial settings it has broadened to mean any undesired delay in the signal chain, whether electrical, mechanical, or software in origin. When latency becomes predictable and is built into specifications, it stops being a problem and becomes a design parameter.