Precision test frequency generator

• US 3,992,680 A
• Filed: 07/30/1975
• Issued: 11/16/1976
• Est. Priority Date: 07/30/1975
• Status: Expired due to Term

• Current Assignee: Fischer & Porter Comapny (ABB Limited)
• Original Assignee: Fischer & Porter Comapny (ABB Limited)
• Inventors: Herzl, Peter J.
• Primary Examiner(s): Kominski, John
• Application Number:
  US05/600,318
• Time in Patent Office: 475 Days
• Field of Search: 328/186, 328/14, 328/165, 331/51, 331/61
• US Class Current: 331/61
• CPC Class Codes: H03K 4/026 using digital techniques

Abstract

A precision test frequency generator capable of selectively providing a sinusoidal output wave within a frequency range simulating the output of a flowmeter yielding a sinusoidal signal whose frequency is proportional to flow rate, the signal having a noise component superimposed thereon. The generator is constituted by a stable high-frequency standard coupled to a selectable output counter providing intermediate-frequency pulses whose repetition rate is a sub-multiple of the high-frequency standard and a predetermined multiple of the desired output frequency of the generator. The pulses are converted into a triangular wave whose frequency corresponds to the desired output frequency, the triangular wave having a staircase formation whose number of steps is determined by the multiple. The triangular wave is converted into a sinusoidal wave of the same frequency with a staircase modulation component simulating the flowmeter output signal.

Claims

1. A precision test generator producing sinusoidal output waves in a predetermined range to simulate the output of an instrument yielding a sinusoidal signal within said range, said sinusoidal signal having a noise component superimposed thereon, said test generator comprising:

A. a stable-frequency standard having a predetermined high-frequency;

B. means coupled to said standard to divide the frequency thereof to produce intermediate frequency pulses whose repetition rate is a selected sub-multiple of said high frequency and a predetermined multiple of the desired output frequency of the test generator within said range, said divider means being constituted by a multi-stage counter provided with a multi-contact selector switch whose contacts are connected to the respective stages of the counter to derive pulses of the desired repetition rate;

C. a triangle generator responsive to said pulses to produce a triangular wave whose frequency corresponds to the desired output frequency, said triangular wave having a staircase formation whose number of steps is determined by said multiple; and

D. means coupled to said triangle generator to transform said triangular wave into a sinusoidal output wave of the same frequency with a staircase component simulating said signal.

2. A test generator as set forth in claim 1, wherein said standard is a crystal-controlled oscillator.

3. A test generator as set forth in claim 1, wherein said high-frequency is about 30,000 Hz.

4. A test generator as set forth in claim 3, wherein said test generator produces output frequencies in the range of 1 to about 2000 Hz.

5. A test generator as set forth in claim 1, further including an interface network coupled to said transforming means to interface said sinusoidal output wave with particular forms of flowmeters.

6. A test generator as set forth in claim 1, wherein said triangle generator includes a ladder network of resistors having different values, and means including a counter responsive to said pulses to selectively connect said resistors to a voltage source to produce an output voltage which progressively rises to create the ascending steps of the staircase and then progressively falls to create the descending steps thereof.

7. A test generator as set forth in claim 6, wherein said means for selectively connecting the resistors to the source is constituted by gate logic units associated with said counter.