MEASUREMENTS

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Waveform Distortions & Measurement Methods 13
I. VIDEO AMPLITUDE & TIME <strong>MEASUREMENTS</strong> This section deals with two fundamental properties of the signal: amplitude and time. In these two dimensions, problems are more frequently caused by operator error than by malfunctioning equipment. Correction of amplitude and pulse width problems often simply involves proper adjustment of the equipment the signal passes through. Two kinds of amplitude measurements are important in television systems. Absolute levels, such as peak-to-peak amplitude, need to be properly adjusted. The relationships between the parts of the signal are also important. The ratio of sync to the rest of the signal, for example, must be accurately maintained. When setting video amplitudes, it is not sufficient to simply adjust the output level of the final piece of equipment in the signal path. Every piece of equipment should be adjusted to appropriately transfer the signal from input to output, since television equipment is generally not designed to handle signals which deviate much from the nominal 1 -volt peak-to-peak amplitude. Signals which are too large can be clipped or distorted, and signals which are too small will suffer from degraded signal-tonoise performance. Video amplitudes are monitored and adjusted on a daily basis in most television facilities, but sync pulse widths tend to be checked less often. It is still important, however, to understand time measurement methods. You should periodically verify that all pulse widths and rise times are within the recommended limits, and adjust them if necessary. This booklet does not address system timing issues, which deal with relative time relationships between the many signals in a television facility. Although system timing is critical to production quality, it is outside the scope of this publication. On the following pages, only those timing measurements which relate to a single signal are addressed. 14
Page 1 and 2: TELEVISION MEASUREMENTS PAL SYSTEMS
Page 3 and 4: About the Author Margaret Craig is
Page 5 and 6: Preface To characterise television
Page 7 and 8: Good Measurement Practices Waveform
Page 9 and 10: Good Measurement Practices Automati
Page 11: Good Measurement Practices Governme
Page 15 and 16: Amplitude Measurements Once you hav
Page 17 and 18: Time Measurements • DEFINITION Ho
Page 19 and 20: Time Measurements Figure 16. The H
Page 21 and 22: SCH Phase • TEST SIGNALS SCH phas
Page 23 and 24: II. LINEAR DISTORTIONS Waveform dis
Page 25 and 26: Chrominance-to-Luminance Gain & Del
Page 27 and 28: Chrominance-to-Luminance Gain & Del
Page 29 and 30: Short Time Distortion • DEFINITIO
Page 31 and 32: Line Time Distortion M DEFINITION L
Page 33 and 34: Field Time Distortion • DEFINITIO
Page 35 and 36: Long Time Distortion • DEFINITION
Page 37 and 38: Frequency Response Modulated sine-s
Page 39 and 40: Frequency Response Figure 47. A swe
Page 41 and 42: Group Delay Figure 51. The Multipul
Page 43 and 44: K Factor Ratings • DEFINITION The
Page 45 and 46: K Factor Ratings The external 1481/
Page 47 and 48: Differential Phase Figure 63. Modul
Page 49 and 50: Differential Phase Two different ty
Page 51 and 52: Differential Gain Figure 71. A Modu
Page 53 and 54: Differential Gain B-Y Sweep Some ve
Page 55 and 56: Luminance Non-Linearity Figure 80.
Page 57 and 58: Chrominance Non-Linear Phase Figure
Page 59 and 60: Chrominance Non-Linear Gain • NOT
Page 61 and 62: Transient Sync Gain Distortion •
Page 63 and 64:
IV. NOISE MEASUREMENTS The electric
Page 65 and 66:
Signal-to-IMoise Ratio To configure
Page 67 and 68:
ICPM • DEFINITION ICPM (Incidenta
Page 69 and 70:
Depth of Modulation Figure 107. Dep
Page 71 and 72:
GLOSSARY OF TELEVISION TERMS DC RES
Page 73 and 74:
APPENDIX A: PAL COLOUR BARS There a
Page 75 and 76:
APPENDIX B — SINE-SQUARED PULSES
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MEASUREMENTS

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