All feedback control systems operate from the error signal which is generated by a comparison of the reference and the output. Error detectors perform the crucial task of comparing the reference 'and output signals. In a purely electrical system where the reference and output are voltages, the error detector is a simple comparator. In some other systems with non-electrical outputs, the output signal is converted into electrical form through a measurement or transducer block, and then error detection is performed on the electrical signals. A position control system, with both input and output variables as mechanical positions (linear or angular), may however consist of two potentiometers -reference and output, which function as an error detector. Other devices which could be used in similar applications include synchro sets (for a,c. systems), sine-cosine potentiometers, hall effect-potentiometers etc, which unfortunately are not readily available.
Experiments
- Linearity study of the error detector.
- Determination of error detector gain.
- Use of a.c. supply for the error detector- introduction to the phase reversal of error signal.