52 U8001A/U8002A User’s and Service Guide
5Service Guide
CV Noise
CV noise is specified as the RMS or peak- to- peak output voltage
in the frequency range from 20 Hz to 20 MHz.
Procedures:
1 Power off the power supply and connect the output to be
tested as shown in Figure 5- 2(C) to a differential amplifier
and load resistor (10
Ω for U8001A and 6 Ω for U8002A)
2 Power on the power supply.
3 When the display is in the limit mode, program the output
voltage to full rated value, i.e. 30 V and output current to the
maximum programmable value.
4 Enable the output of the power supply.
5 Make sure that the power supply is in CV mode. If not, adjust
the resistive load so that the output current drops slightly
until the power supply is in CV mode.
6 Configure the differential amplifier as follow:
• Set to AC mode (positive and negative) to removes the DC
component
• Set to differential mode
• Set gain to x10
• Set attenuation to 1
• Set low pass filter to 20 MHz bandwidth limit to filter out
input signal which contains higher frequency
• Set to zero precision voltage generator
• Set input impedance to 1 M
Ω
7 Configure the scope as follow:
• Set time range to 50 ms (20 Hz)
• Acquires every single sample at the maximum sampling
rate and retains only the min and max values in a
"sampling region" (50 ms time range)
• Enable 20 MHz cut off frequency for better high frequency
cut- off
• AC coupling
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