Unigraf VLM-333 User manual

VLM-333 User’s Manual
123UNIGRAF
UNIGRAF OY
Ruukintie 3
Fin-02330 Espoo
Finland
Tel: [phone]
Fax: [phone]
Www.unigraf.fi

Table of Contents:
Description of VLM-333 3
Specification 4
Battery replacement 5
Calibration 6

UNIGRAF VLM-333 is a hand held RGB video level meter that simultaneously
measures and displays the amplitude of all the three componenets of an RGB
video signal. Featuring a basic accuracy of 0.3% or better, the VLM-333 can be
used to quickly and easily measure the video levels wherever and whenever
necessary.
The video input connectors of the VLM-333 are 3 pcs BNC and a HDD-15P (VGA
compatible) connector. They are internally coupled together and terminated with
75 ohm precision (0.1%) resistors.
The VLM-333 can be powered by the internal batteries, external source and
through the 15 pin connector from the DDC +5Volt source. When driven by the
DDC source the power switch has no effect and the unit will continue to stay
switched on.
For a correct measurement it is necessary that the measured video
signal contains only 3 usec or longer periods of white, each followed by
3 usec or longer period of black. A typical picture fulfilling this
requirement is such where the left half of the screen is white and the
right half is black. The horizontal frequency range is 10 - 120 kHz. The
presence/absence of sync pulses in R, G or B do not affect the
measurement. The VLM-333 can be used to measure a single video
signal as well, in such case the signal must be connected at the G
input. The display of VLM-333 will indicate when a signal with sufficient
amplitude is applied in the G input.
The VLM-333 will only make measurements on fields of white. It will not
make a measurement when a crosshatch or text is present. This is
done to guarantee a precise reading without concern for video peaking
or other distortion.
Making Measurements
Product Description
Page 3

Measuring range: 300 - 1200 mV
Input voltage range:-0.150V to +2.0V
Input impedance: 75 ohm ± 0.2% per channel
Reading accuracy: ± 0.3%, ± 1 digit
Power supply: Internal batteries (4 AA) or an external DC adapter 6.5 - 12V
or AC adapter 7.5-12V, it can also be powered by the +5V DDC
from the VGA connector
30 mA (100 mA max with back light on)
Size: height 96 mm x width165 mm x depth 33 mm, without handle
(120x180x33 with handle)
Weight: 800 g
Technical Specifications
Front panel and connectors
123UNIGRAF VLM-333
Video Level Meter
ON OFF
Back
Light
R G B VGA
Video Inputs
DC in 6.5-12V
or
AC in 7.5-12V
Back Light
Switch
Power On-Off
Switch
HDD-15pin
Input Connector
BNC
Input Connectors
External Power
Input Connector
LCD
Display
Page 4

Battery Removal and Replacement
1. Turn off power
2. Loosen 2 handle thumb screws
3. Loosen 8 end screws (it is not
necessary to remove them)
4. Remove back cover (batteries can
also be accessed from the front)
5. Remove battery carrier
6. Replace the 4 AA batteries with
Alkaline or better grade battery
7. Replace the battery compartment
and back cover.
8. Tighten the 8 end screws and 2
handle thumb screws
Page 5

VLM-333 Calibration
The VLM-333 is a precision instrument and should be calibrated
once per year. It is recommended that the calibration be done at
the factory. If this is not possible then it will be necessary to have a
signal source that can generate a stable pulse of the proper
durations of 3usec with 50% duty cycle. To make the
measurement traceable the source will need to be checked in
both the low and high state with a precision traceable DVM. The
VLM-333 is AC coupled so the difference of the two level will be
the readout adjusted on the VLM-333. Preferably this level should
be 700mV peak to peak. The RGB inputs have independent
adjustment controls as seen in the picture below. The other
adjustment is for the LCD viewing angle.
LCD Viewing angle adjust
Red Level adjust Blue Level adjust
Green Level adjust
Page 6