Sample and Hold
A component of a type of analogue-to-digital converter. The analog signal is frozen in a sample and hold circuit to prevent it changing during digitization.
The number of samples, or readings, per second of an analog signal.
Normal channel scanning in a data acquisition system involves stepping around and reading each input channel in turn. The scan will return to the first channel once all the channels have been sampled.
Supervisory control and data acquisition – a large scale software package usually used to monitor and control a manufacturing process.
The principle that describes how a thermocouple works. In a circuit in which there are junctions between dissimilar metals, an electromotive force (voltage) is set up when the junctions are at different temperatures.
A data acquisition module with a stable on-board reference voltage that software can use for automatic recalibration.
A measure of the minimum change in an input signal that an instrument can detect.
A device that can detect a change in a physical quantity and produce a corresponding electrical signal.
Where data is transferred one bit at a time.
When a change in signal occurs, the time taken for the input or output channel to settle to its new value.
The value of a controlled variable, a departure from which causes a controller to operate to reduce the error and restore the intended steady state.
The International system of units. Abbreviation for Systeme International.
Makes a signal suitable for input to an analogue-to-digital converter. For example, a signal may be filtered to remove noise, or amplified to meet the range of the A-D converter.
A general term referring to a conveyor of information.
Signal to Noise Ratio
Compares the signal strength to background noise. Abbreviated to SNR or S/N. The ratio is usually measured in decibels (dB).
An analog input that is measured with respect to a common earth. Single-ended inputs are only suitable for signals that are of good size – 100 mV full scale or above.
When all analog signals are read simultaneously. This is achieved by providing each input with its own A-D converter, and initiating sampling from a single clock. It ensures that there is no reduction in sampling rate when more signals are connected.