Service Guide 5
U8001A/U8002A User’s and Service Guide 61
CC Noise
CC noise is specified as the RMS output current in a frequency
range 20 Hz to 20 MHz with the power supply in constant
current operation.
Procedures:
1 Power off the power supply and connect the output to be
tested as shown in Figure 5- 2(D) to an AC/DC converter 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 maximum programmable value and output current
to full rated value, i.e. 3 A for U8001A and 5 A for U8002A.
4 Enable the output.
5 Make sure that the power supply is in CC mode. If not, adjust
the resistive load so that the output voltage drops slightly
until the power supply is in CC 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 RMS voltmeter as follow:
• Set high pass filter to10 Hz
• AC coupling
8 Divide the reading of the RMS voltmeter by 10 and then
multiply the result by 5 to get the RMS noise measurement.
The result should not exceed the RMS limits of 3 mA
RMS
.
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