Apparatus including a selectively connectable isolation transformer for determining the speed and direction of a rotating object

An apparatus for determining the rotational speed and direction of a rotating object, wherein the apparatus has a circuit ground and power, the apparatus further comprising:

• a sensor having a sensor ground and being adapted to detect the speed and direction of the rotating object and responsively produce an input frequency signal having a frequency proportional to the rotational speed of the rotating object and a direction signal having a voltage value indicative of the rotational direction of the rotating object;
• a common terminal;
• a transformer adapted to receive the input frequency signal and electrically isolate the sensor ground from the circuit ground;
• double-pole, double-throw switch means coupling the input frequency signal through said transformer to said common terminal in a first position of said switch means, and, bypassing said transformer, connecting said sensor ground to circuit ground, and coupling said input frequency signal directly to said common terminal in a second position of said switch means;
• means for receiving said input frequency signal from said common terminal, and responsively producing a conditioned frequency signal having a pulsed waveform wherein each pulse is defined by a rising edge and a falling edge;
• distinguishing means for receiving said conditioned frequency and direction signals, determining the voltage value of a portion of said direction signal that coincides with the falling edge of said conditioned frequency signal, and responsively producing a control signal having a voltage level responsive to the determined voltage value of said direction signal;
• converting means for receiving said conditioned frequency signal and responsively producing an output signal having a DC voltage proportional to the frequency of said conditioned frequency signal;
• directional means for receiving the control signal and the output signal, and changing the polarity of the output signal in response to the voltage level of said control signal;
• and
• an output device adapted to receive the polarized output signal, and responsively store the magnitude and polarity of the output signal for subsequent analysis.