1. Field of the Invention
The subject matter of this invention relates generally to electrical circuits for checking tachometers and relates more specifically to electrical circuits which are utilized to determine whether a tachometer is correctly wired internally and whether it is providing the expected output voltage when it is utilized in a motor controller application.
2. Description of the Prior Art
The use of electrical tachometers is well known. In particular, an electrical tachometer is essentially a voltage generator which is interconnected with the shaft of a rotating device and calibrated to produce a voltage output which is related to the speed of the device. In some instances, this voltage output signal is fed back to an electrical control system which in turn is utilized to monitor, check or otherwise control the speed of the device being monitored by the tachometer. A disadvantage with the aforegoing mentioned system lies in the fact that the integrity of the tachometer is an integral part of the closed loop and if the tachometer is providing an improper or erroneous signal, action may be taken by the control signal which is inappropriate or even dangerous. It will be advantageous therefore if apparatus or circuitry could be found which could be utilized in conjunction with the closed loop system which includes the tachometer to determine the reliability of the tachometer for accomplishing its desired purpose.