Field test instrument

• US 5,225,768 A
• Filed: 03/13/1992
• Issued: 07/06/1993
• Est. Priority Date: 03/13/1992
• Status: Expired due to Fees

• Current Assignee: Mannesmann Kienzle GmbH (HP Inc.)
• Original Assignee: Mannesmann AG (Vodafone Group PLC)
• Inventors: Reaves, Samuel H. III
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Solis, Jose M.
• Application Number:
  US07/850,576
• Time in Patent Office: 480 Days
• Field of Search: 331/25, 377/29, 324/83 D, 324/161, 324/78 D, 324/79 R, 324/79 D
• US Class Current: 324/76.47
• CPC Class Codes: G01P 21/02 of speedometers
• CPC Class Codes: G07B 13/00 Taximeters measuring distance travelled G01C; measuring time G04
• CPC Class Codes: G07C 5/0808 Diagnosing performance data testing of vehicles G01M17/00; testing of electrical installation on vehicles G01R31/005

Abstract

A calibration generator for furnishing signals to tachographs, taximeters and other instruments used in fleet management systems. Calibrated frequencies and amplitudes are provided by the generator of the invention. A PLL controlled synthesizer, driven by a crystal oscillator, supplies frequencies under control from the operator. An alternative continuously controlled oscillator is also available for tests.

Claims

1. A testing apparatus comprising

a phase-locked loop signal source having an output;

a variable oscillator source having an output;

a mode switch having a first terminal connected to the output of the phase-lock loop signal source, and having a second terminal connected to the variable oscillator source for selecting between the output of the phase-locked loop signal source and the variable oscillator source, and having an output terminal;

an output buffer receiving a signal derived from the output terminal of the mode switch for connecting to a monitoring device;

a variable output buffer receiving a signal derived from the output terminal of the mode switch for providing a test signal output;

a selector switch having a first terminal connected to the output terminal of the mode switch, having a second terminal to be connected to an external source, and having a third terminal;

a pulse and frequency counter connected to the third terminal of the selector switch;

a readout connected to the pulse and frequency counter.

2. The testing apparatus according to claim 1, wherein the phase-locked loop signal source includes

a reference oscillator generating a reference signal;

a phase comparator having a first input connected to the reference oscillator, having a second input, and having an output delivering a direct current output voltage;

a voltage controlled oscillator having an input connected to the output of the phase comparator, and having an output connected to the first terminal of the mode switch;

a range switch;

a divider controlled by the range switch and having an input connected to the output of the voltage controlled oscillator and having an output connected to the second input of the phase comparator.

3. The testing apparatus according to claim 1, wherein the variable oscillator source includes

a variable frequency oscillator having a control input and having an output connected to the second terminal of the mode switch;

a potentiometer connected to the control input of the variable frequency oscillator.

4. The testing apparatus according to claim 1, wherein the pulse and frequency counter includes

a pulse/frequency counter module connected to the third terminal of the selector switch, and having an output terminal, having a reset terminal, and having a selector terminal;

a second switch connected to the selector terminal of the pulse/frequency module for selecting between pulse count and frequency count operation;

a display reset switch connected to the reset terminal;

a counter gating logic having an input connected to the pulse/frequency counter module, having a switch terminal, and having an output;

a first switch connected to the switch terminal for selecting between displaying continuously or holding a display;

a precision crystal oscillator and divider circuit configured to control the counter gating logic.

5. The testing apparatus according to claim 1, further comprising

an input amplifier having an input to be connected to an external source, and having an output connected to the second terminal.

6. The testing apparatus according to claim 1, further comprising

an input amplifier having an input to be connected to the variable oscillator source, and having an output connected to the second terminal.

7. The testing apparatus according to claim 2, further comprising

an input amplifier having an input to be connected to the reference oscillator, and having an output connected to the second terminal.

8. The testing apparatus according to claim 5, further comprising

shielding means for shielding the input amplifier against interfering electromagnetic signals.

9. The testing apparatus according to claim 5, further comprising

a grounding line substantially surrounding the input amplifier for suppression of interference pickup by the input amplifier.

10. The testing apparatus according to claim 5, wherein the input amplifier is provided by a transistor, wherein a first terminal of the transistor is the base of the transistor and is to be connected to the external signal source, wherein a second terminal of the transistor is connected to ground, and wherein lines connected to the second terminal substantially surround the first terminal and a third terminal of the transistor.

11. The testing apparatus according to claim 5, wherein the input amplifier is provided by a transistor, wherein a terminal of the transistor is connected to lines substantially surrounding two other terminals of the transistor.

12. The testing apparatus according to claim 1, further comprising

a voltage divider having an input connected to the output of the selector switch, and having an output connected to the output buffer.

13. The testing apparatus according to claim 1, wherein the output buffer is adapted for connection to a vehicle monitoring apparatus.

14. The testing apparatus according to claim 1, further comprising

a potentiometer having a resistor connected to ground and to the output of the selector switch, and having a tap for determining a signal output level, wherein the variable output buffer is connected to the tap of the potentiometer for providing a test signal output at a desired voltage amplitude level.

15. The testing apparatus according to claim 1, further comprising

a selection switch connected to the output buffer for selecting a test signal type to be provided to a commercial vehicle monitor.

16. The testing apparatus according to claim 1, further comprising

status switches connected to the output buffer for determining an operational state of a commercial vehicle monitor during testing.

17. The testing apparatus according to claim 1, further comprising

indicator lamps connected to the output buffer for indicating the kind of signals provided to and from a commercial vehicle monitor.

18. The testing apparatus according to claim 1, further comprising

a multiplier switch connected to the phase locked loop signal source for multiplying the frequency provided by the phase-locked loop signal source.

19. The testing apparatus according to claim 1, further comprising

a printed circuit board, wherein the phase-locked loop signal source, the variable oscillator source, the mode switch, the output buffer, the variable output buffer, the selector switch, and the pulse and frequency counter are furnished on the printed circuit board.

20. The testing apparatus according to claim 1, further comprising

a pulse and frequency counter having an input and connected with an input amplifier having an output connected to the third terminal of the selector switch, wherein the output of the input amplifier is connected to the input of the pulse and frequency counter, said input amplifier having an input connected to the third terminal of the selector switch;

a readout connected to the pulse and frequency counter.

21. The testing apparatus according to claim 20, further comprising

an input jack connected to the first terminal of a selector switch allowing a selection of an external source of pulses or frequency;

wherein the second terminal of the selector switch for selecting the pulse and frequency source is either phase locked or variable internal to the apparatus.

22. The testing apparatus according to claim 20, further comprising

an input amplifier, wherein the third terminal is connected to the input amplifier, and wherein the output of the input amplifier is connected to the input of the pulse and frequency counters.

23. The testing apparatus according to claim 20, further comprising

a readout display connected to the pulse and frequency counters.