Velleman DVM20FGC Guia De Inicio Rapido página 3

12. VCF IN
13. PULL TO VAR DC OFFSET
14. TTL/CMOS OUT
15. PULL TO TTL CMOS LEVEL
16. OUTPUT
17. ATTENUATOR
18. PULL TO INV AMPLITUDE
4. Calibration & Maintenance
The device can work continuously under normal conditions. Calibrate it every months to
guarantee precision. Proceed as follows :
Sine wave distortion adjustment : press the buttons RAMP/PULSE slope (11) and DC offset
(13) and select the "1k" frequency range. The displayed frequency is "5KHz" or "2KHz". Adjust
potentiometers RP105, RP112, RP113 slowly in order to minimise distortion. Select a frequency
of 500Hz or 200Hz with the frequency potentiometer and adjust pot RP104 to minimise
distortion. Repeat this procedure for the entire range using the 6 other range buttons. This will
allow you to limit the distortion for the entire range (10Hz~100KHz) to less than 1%.
Square wave response : set the operating frequency to 1MHz and optimise the transient
response of the signal with capacitor C174.
Counter accuracy adjustment : put the counter in the EXT position and connect it with the
10MHz output signal of a standard oscillator. Select a gate time of 0.01s and adjust C214 until
the display indicates 10000.0KHz.
Counter sensitivity adjustment : connect a sine wave of 100mVrms/10MHz generated by the
signal generator to the external counter. Select a gate time of 0.01s and adjust RP115 until the
display reads 10000.0KHz.
5. Faults
Contact your dealer if the device does not work as it should. Do NOT try to repair the device
yourself.
6. Accessories
• instruction manual
• input cable
DVM20FGC
slope of the ramp and the duty cycle of the pulse can
also be adjusted.
: This input is used to control the frequency through an
external source.
: With this knob in the pulled-out position you can set the
DC voltage of any waveform. Turn clockwise (+) or
counterclockwise (-). The DC voltage is 0 when the
button is in the pressed-down position.
: The output waveform is a TTL/CMOS pulse that can also
be used as a synchronising signal.
: Pull this knob out for a TTL output or press it down for an
adjustable CMOS signal.
: This rotary control provides the output signal for all
waveforms. The output impedance is 50Ω.
: Press one of the buttons for either 20 or 40dB
attenuation.
: When the button is in the pulled-out position, it can invert
the polarity of the output signal in combination with (11).
It can also adjust the output amplitude.
power cord
fuse (0.5A)
3
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