Dorrough VLM-40 NTSC Technical Instruction Manual Download | Manualshive

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COMPOSITE VIDEO LUMINANCE METER

MODEL VLM-40

-48

-40

0

20

40

60

80

100

120

© 1990

SYNC

LUMINANCE

IRE UNITS

-32

SYNC

SETUP

C

OMPOSITE

V

IDEO

L

UMINANCE

M

ETER

M

ODEL

VLM-40 NTSC

T

ECHNICAL

I

NSTRUCTION

M

ANUAL

1
2
3
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Summary of Contents for VLM-40 NTSC

Page 1: ...COMPOSITE VIDEO LUMINANCE METER MODEL VLM 40 48 40 0 20 40 60 80 100 120 1990 SYNC LUMINANCE IRE UNITS 32 SYNC SETUP COMPOSITE VIDEO LUMINANCE METER MODEL VLM 40 NTSC TECHNICAL INSTRUCTION MANUAL...

Page 2: ...ret data on the single meter scale The VLM 40 is insensitive to chroma information VITS vertical interval test signals and it responds to luminance signals as short as 200 ns in length INPUT IMPEDANCE...

Page 3: ...ncludes sync and setup LEDs that detect the status of these corresponding video levels Under normal operating conditions the sync LED will be green whenever the video source has a proper sync signal I...

Page 4: ...be installed in an optional panel mount e g DORROUGH Rack Mount Kit 40 S for a single meter or 40 D for dual meters or operated as a stand alone package The remainder of this Technical Instruction Man...

Page 5: ...VLM 40 refer to Fig 3 for mounting dimensions Choose a ventilated area that provides a minimum depth of 10 for proper cable routing Consider a location that not only will offer easy observation of the...

Page 6: ...eo BNC connector on the back panel Select Term or Hi Z to terminate the connection 4 Feed a standard EIA split field color bar signal with standard setup at 140 IRE 1 V p p to the VLM 40 and verify th...

Page 7: ...ture tube as shown in Fig 5 The synchronization signals embedded in the television signal precisely instruct the electron beam to move across and down the picture tube to build a complete picture usin...

Page 8: ...ve picture lines occurring after 21 lines of vertical blanking For PAL SECAM measurements contact the the factory for information on the VLM 40 PAL SECAM meter 1 Using a standard television test signa...

Page 9: ...60 40 20 20 40 0 setup 7 5 COMPOSITE VIDEO LUMINANCE METER MODEL VLM 40 48 40 0 20 40 60 80 100 120 1990 SYNC LUMINANCE IRE UNITS 32 SYNC SETUP COMPOSITE VIDEO LUMINANCE METER MODEL VLM 40 48 40 0 20...

Page 10: ...k luminance on a waveform monitor as shown in Fig 10 NOTE The VLM 40 is very sensitive to measuring noise in the luminance signal and will respond to short impulses that may be undetected on a standar...

Page 11: ...in Fig 12 The thresholds are Setup Level Setup LED Above 7 5 IRE Green 7 5 to 4 0 IRE Green Below 4 0 IRE Red COMPOSITE VIDEO LUMINANCE METER MODEL VLM 40 48 40 0 20 40 60 80 100 120 1990 SYNC LUMINA...

Page 12: ...E IRE UNITS 32 SYNC SETUP IRE Units 100 80 60 40 20 20 40 0 setup 7 5 Fig 12 On the VLM 40 the sync LED flashes red each time a sync pulse is missing You may not easily detect this fault using a wavef...

Page 13: ...vel is less than 4 IRE IRE Units 100 80 60 40 20 20 40 0 setup 7 5 COMPOSITE VIDEO LUMINANCE METER MODEL VLM 40 48 40 0 20 40 60 80 100 120 1990 SYNC LUMINANCE IRE UNITS 32 SYNC SETUP Fig 15 On the VL...

Page 14: ...VLM 40 the average luminance levels are below 40 IRE and the peak LED indicates peak luminance levels are at 60 IRE The waveform monitor shows peak luminance levels just above 60 IRE but calculating a...

Page 15: ...on the termination switch SW1 Set the waveform generator to split field bar pattern 100 white flag 3 Apply power to the VLM 40 Adjust the rear panel input level control VR 13 so that the 100 IRE peak...

Page 16: ...n 15 Fig 17 This simplified circuit board diagram shows key components used to calibrate the VLM 40 for NTSC operation VLM 40 NTSC TECHNICAL INSTRUCTION MANUAL CALIBRATION TRANSFORMER J2 J1 VR36 U7 U3...

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