PHASEMETERING SYSTEM INCLUDING NOISE COMPONENT CORRECTING MEANS

• US 3,622,879 A
• Filed: 05/04/1970
• Issued: 11/23/1971
• Est. Priority Date: 05/12/1969
• Status: Expired due to Term

• Current Assignee: Andre Girouy, Gerard D'Auzac, Jean Douzon, Paul Zagigaeff
• Original Assignee: Andre Girouy, Gerard D'Auzac, Jean Douzon, Paul Zagigaeff
• Inventors: Zagigaeff, Paul, Girouy, Andre, D'Auzac, Gerard, Douzon, Jean
• Primary Examiner(s): Smith, Alfred E.
• Application Number:
  US05/034,142
• Time in Patent Office: 568 Days
• Field of Search: 324/83D,186,187
• US Class Current: 324/76.82
• CPC Class Codes: G01R 25/00 Arrangements for measuring phase angle between a voltage and a current or between voltages or currents
• CPC Class Codes: H03M 1/50 with intermediate conversion to time interval H03M1/64 takes precedence

Abstract

In a digital phasemeter of the type comprising an input stage for generating gating signals having duration Pi proportional to the phase-shift between two signals, and a computer for averaging the n signals Pi obtained in the course of n successive measurement, a correcting circuit is provided for compensating the errors equal in absolute value to T affecting the duration of the gating signals when, because of noise, a small real phaseshift (near zero) has given rise to a long gating signal (near T) or a large phase-shift (near 2 pi ) to a short gating signal (near zero).

Claims

1. A digital phasemeter for measuring the phase-shift Delta phi (0 Delta phi <

2 pi ) of a nominally periodic input signal in relation to a reference phase signal of the same periodicity T, comprising;

an input stage, having an output, for the production, from the input signal and the reference signal, of gating signals of duration Pi equal to the time interval separating two homologous zero points in the input and reference signals;

a clock, having an output, for delivering pulses of recurrence frequency F No/T, where No is a positive integer;

a gating device comprising a signal input connected to said output of said clock, a control input coupled to said output of said input stage, and an output, for transmitting the pulses from said clock only in the presence of said gating signals;

a computer device coupled to said output of said gating device, for delivering, for each measurement cycle corresponding to the production of n gating signals where n is a positive integer, a number, equal, module No, to the whole number part of the quotient S/n, where;

S R+N1+N2+ ...+ Nn Ni (i 1, 2... n) being the number of pulses transmitted by said gating device during the time of the gating signal Pi, and R a number determined by the initial state of the memory elements of the computer device;

a correcting circuit having;

an output coupled to said computer device;

first means for applying to said computer device, at the end of a measurement cycle, pulses, referred to as correction pulses, with the effect that number N is automatically substituted by a number N'"'"''"'"' which is equal, modules No, to the whole number part of the quotient S'"'"''"'"'/n, where S'"'"''"'"' is equal to S+(n-m)No, where m is the number of said gating signals whose duration exceeds a predetermined duration L smaller than T; and

second means for authorizing or inhibiting the operation of said first means as a function of at least one criterion concerning the distribution of said n gating signals into three categories, the first of which comprises the gating signals, whose duration does not exceed a given value Alpha , the second of which comprises the gating signals whose duration exceeds Alpha without exceeding a given value Beta greater than Alpha , and the third of which comprises the signals whose duration exceeds Beta , Alpha and Beta being two durations smaller than T, one of which is equal to said duration L.

2. A digital phasemeter as claimed in claim 1, wherein said second means are designed for authorizing or inhibiting the operation of said first means as a function of a single criterion, which is the presence, among said n gating signals, of at least one gating signal in a predetermined one of said categories.

3. A digital phasemeter as claimed in claim 1, wherein said two numbers n and No being such that one is a multiple of the other:

said computer device comprises in series a divider by 1/n having an input connected to the output of said gating device, and a counter counting from zero to No-1 and returning thereafter to zero, and wherein said computer device comprises an auxiliary output connected to the output of said correcting circuit and such that a pulse applied to said auxiliary output affects the number delivered by said counter in the same way as No pulses applied to said input of said divider.

4. A Phasemeter as claimed in claim 1, wherein said first means of said correcting circuit comprise a further counter counting from 0 to n-1 and returning thereafter to zero;

means for applying to said further counter a pulse for each gating signal whose duration is greater than said duration L;

a pulse source having an output;

means for coupling said output of said pulse source, at the end of a measurement cycle, both to said computer device and to said further counter; and

means for disconnecting said pulse source from said computer device when said further counter returns to zero.

5. A phasemeter as claimed in claim 2, wherein said value L is equal to Alpha , and wherein said second means are designed to authorize the operation of said first means when said n gating signals comprise at least one gating signal of duration longer than Beta .

6. A phasemeter as claimed in claim 1, wherein said input stage further comprises means for generating, for each gating signal of duration Pi, a further signal P'"'"''"'"'i of duration kT-Pi, where k is a predetermined integer, and means allowing the substitution of P'"'"''"'"'i for Pi on said output of said input stage.