Measurement-computing DBK80 Manuel d'utilisateur télécharger pdf (Page 3)

Three examples of using the excitation source follow. They are Position Sensing, Resistance/Thermistor

Measurement, and Reading a Transducer.

Source Impedance and Settling Time

High speed multiplexing of signal sources with non-zero impedance will result in reading errors caused by

settling time. In the simplest form, a multiplexing system consists of a group of switches, with internal

resistance, and an output capacitance at the input of an amplifier feeding an A/D converter with a sample-

hold circuit on the input. During the short time a channel signal is connected to the A/D amplifier, the

signal must charge the output capacitance to the true value of the signal so that the sample-hold captures an

accurate value for the A/D converter to digitize. If the source has significant internal impedance the

voltage reading will be reduced.

DBK Option Cards and Modules 989494 DBK80 pg. 3

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Measurement-computing DBK80 Manuel d'utilisateur Page 3