Vertical tracking angle meter
AssigneeCBS Inc.
InventorsLouis A. Abbagnaro, Arthur J. Gust
Life of this patent
Estimating the term…
Abstract
Measuring instrument which extracts and directly displays the vertical tracking angle of a phonograph pickup during playback of a known test record signal, and which also has the capability of measuring and directly displaying tracing distortion.
Claims10
Apparatus for use with a test record having a test signal recorded thereon consisting of low and high audio frequency sinusoidal signals differing in frequency by a factor of about ten recorded together with a known recording angle, for measuring at least the tracking angle of a phonograph pickup during playback of said test signal, said apparatus comprising:
- means for applying the test signal transduced from the test record by the pickup under measurement to first and second signal paths,
- said first signal path including discriminator means for producing a deviation signal at said low frequency of amplitude proportional to the frequency deviation produced at the stylus tip of said pickup due to mismatch between the tracking angle of said pickup and said known recording angle and to tracing distortion, and
- said second signal path including filter means for passing substantially only the low frequency signal transduced from said test record, and means for converting said low frequency signal to a square wave signal which is either in phase or 180.degree. out of phase with respect to said deviation signal when said deviation is due to mismatch between said recording and tracking, angles and which is in quadrature phase relationship with respect to said deviation signal when said deviation is due to tracing distortion;
- means for combining said deviation signal and said square wave signal and producing an output signal which has the characteristics of a full-wave rectified sine wave in response to components of said deviation signal that are either in phase or in phase opposition with respect to said square wave signal and amplitude proportional to the degree of mismatch between said recording and tracking angles, and which is symmetrical and changes polarity each cycle of said square wave signal in response to components of said deviation signal that are in quadrature phase relationship with said square wave signal;
- a voltmeter calibrated to display at least the peak deviation of said deviation signal;
- and
- means connected between said signal combining means and said voltmeter for coupling to said voltmeter only a resultant signal of finite value proportional to the amplitude of an output signal having the characteristics of a full-wave rectified sine wave.
Apparatus for use with a test record having a test signal recorded thereon consisting of 400 Hz and 4 KHz sinusoidal signals recorded together with known signal amplitude and vertical recording angle, for measuring the vertical tracking angle of a phonograph pickup during playback of said test signal, said apparatus comprising:
- means for applying the test signal transduced from the test record by the pickup under measurement to first and second signal paths,
- said first signal path including discriminator means for producing a 400 Hz deviation signal of amplitude proportional to the frequency deviation produced at the stylus tip of said pickup due to mismatch between the vertical tracking angle of said pickup and said known vertical recording angle and also to tracing distortion, and
- said second signal path including filter means for passing substantially only the 400 Hz signal transduced from said record, and means for converting said 400 Hz signal to a square wave signal which is either in phase or 180.degree. out of phase with respect to said deviation signal when said deviation is due to mismatch between said vertical recording and tracking angles and which is in quadrature with said deviation signal when said deviation is due to tracing distortion;
- means for chopping said deviation signal with said square wave signal for producing an output signal having the characteristics of a full-wave rectified sine wave in response to components of said deviation signal that are either in phase or in phase opposition with respect to said square wave signal and having an amplitude proportional to the degree of mismatch between said known vertical recording angle and the vertical tracking angle of said pickup, and for producing an output signal which is symmetrical and changes polarity each cycle of said square wave signal in response to components of said deviation signal that are in quadrature phase relationship with said square wave signal;
- a voltmeter calibrated to display at least the peak deviation of said deviation signal;
- and means connected between said signal chopping means and said voltmeter for rejecting a symmetrical output signal while passing to said voltmeter only a signal having a magnitude proportional to the average value of an output signal having the characteristics of a full-wave rectified sine wave.
Dependencies are inferred from the claim text.