A sensing potentiometer of total resistance has one end of its track on ground and…
PHYSICS · Multi-part · Fermi University Physics · Electronics, Instrumentation & Communication · Circuit foundations and passive networks · Sensors, detectors and experimental instrumentation
Electronics for Measurement, Ch The resistive network: two laws, one equivalent and the loading error
Problem
A sensing potentiometer of total resistance Rpot=47kΩ has one end of its track on ground and the other held at a fixed positive voltage by an ideal source. A data-logger is connected between the wiper and ground; its input resistance is stated on its specification sheet only as "about 2MΩ". As the wiper travels from one end to the other, the resistance looking back into the wiper terminal (with the two ends held at fixed potentials) rises from zero at either end to a maximum at mid-travel, where it equals one quarter of the total track resistance.
((a)) Estimate the largest output resistance the wiper can present to the logger.
((b)) Estimate the largest percentage by which the logger's reading falls below the unloaded wiper voltage, at any wiper position where that voltage is not zero.