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

• US 5,345,171 A
• Filed: 01/11/1993
• Issued: 09/06/1994
• Est. Priority Date: 01/11/1993
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Simmons, Jeffrey J., Love, W. John
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US08/002,558
• Time in Patent Office: 603 Days
• Field of Search: 324/160, 324/163, 324/165, 324/166, 364/565, 340/671, 340/672
• US Class Current: 324/166
• CPC Class Codes: G01P 13/045 with speed indication
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

In one aspect of the present invention, an apparatus determines the rotational speed and direction of a rotating object. The apparatus includes a sensor adapted to detect the speed and direction of the rotating object and responsively produce a frequency signal indicative of the speed of the rotating object and a direction signal having a voltage value indicative of the rotational direction of the rotating object. A distinguishing stage receives the frequency and direction signals, and determines the voltage value of the portion of the direction signal that coincides with the falling edge of the frequency signal. Responsively the distinguishing stage produces a control signal having a voltage level responsive to the determined voltage value of the direction signal. A converting stage receives the frequency signal and responsively produces an output signal having a DC voltage proportional to the frequency of the frequency signal. A directional stage receives the control signal and the output signal, and changes the polarity of the output signal in response to the voltage level of said control signal. An output device receives the polarized output signal, and stores the magnitude and polarity of the output signal.

Claims

1. 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.

2. An apparatus, as set forth in claim 1, wherein said direction signal has a 50% duty factor and is phase shifted 90 degrees with respect to said frequency signal.

3. An apparatus, as set forth in claim 2, wherein said distinguishing means includes:

an inverter adapted to receive said conditioned signal and responsively invert said conditioned signal; and

a D flip-flop having a clock and D input terminals and a Q output terminal, the D flip-flop being adapted to receive said direction signal at the D input terminal and the inverted frequency signal at the clock input terminal, to latch the Q output terminal at the voltage value of said direction signal in response to the rising edge transition of the inverted frequency signal, and to produce said control signal having a voltage level responsive to the voltage value at the Q output terminal.

4. An apparatus, as set forth in claim 3, wherein the directional means includes:

an inverting amplifier adapted to multiply the output signal by a negative gain and produce a negative output signal;

a non-inverting amplifier adapted to multiply the output signal by a positive gain and produce a positive output signal; and

an analog switch adapted to receive the positive and negative output signal and the control signal, pass the positive output signal in response to the control signal having a "high" voltage level, and pass the negative output signal in response to the control signal having a "low" voltage level.

5. An apparatus, as set forth in claim 4, including a scaling means for receiving said output signal and selectively amplifying said output signal.

6. An apparatus, as set forth in claim 5, including a filter adapted to receive the polarized output signal and responsively remove predetermined frequency components from the output signal.

7. An apparatus, as set forth in claim 6, wherein said filter includes a second order Butterworth filter.

8. An apparatus, as set forth in claim 7, including a signaling means for receiving the control signal and producing an optical signal in response to the control signal having a "low" voltage level.

9. An apparatus, as set forth in claim 8, wherein said signaling means includes:

an LED connected between the Q output terminal and the circuit ground; and

a P-channel MOSFET transistor having a gate connected to the Q output terminal, a drain connected to the LED, and a source and substrate connected to the circuit power.