S-record

See Motorola S-record format.

S/H

(as letters) abbr. See sample-and-hold.

s/w

(software) abbr. See software.

safety ground

n. A ground connection designed to divert leakages from failed components. Usually also the frame ground, the safety ensures that a loose wire inside the device will cause a short circuit, blowing a fuse or circuit breaker.

Older readers will remember the glory days of beautifully engineered power tools with aluminum cases. Those case were all tied to the AC mains ground. Any internal failure would short to the conductive case, and thus to the mains ground, blowing the fuse. Today these tools are all encased in plastic and often have no ground connection to the mains. The nonconductive case will not conduct a short circuit to the user, so although there s no safety ground, the user is already protected.

safety-critical

adj. Said of a system that could or would cause a human or financial catastrophe if it failed.

sample-and-hold

adj. Said of a circuit that memorizes an analog input. Sometimes abbreviated S&H or S/H. A sample-and-hold circuit stores an analog input in a capacitor when a digital input is asserted. A high-impedance op-amp ensures the cap s voltage remains stable for a reasonable period (milliseconds to seconds, depending on the circuit).

Sample-and-hold behavior is a basic part of most A/D converters.

A typical sample-and-hold circuit. The capacitor latches the analog input.

sampling rate

n. The rate at which a system reads an input (usually analog). The sampling rate largely determines the ability...