Agilent Technologies E364XA Series, User Manual

Page: 190 / 220

Appendix Service Information
Common Mode Current Noise
189
Ser
vice
In
for
mat
ion
1
Turn off the power supply and connect the output to be tested as shown above
with the current monitoring resistor 0.2
9
(R
M2
) across output terminals.
Connect a rms voltmeter across the current monitoring resistor as shown on
the previous page.
2 Turn on the power supply. Select the output to be tested and the low voltage
range (8V/3A)
†
, enable the output, and set the display to the limit mode. When
the display is in the limit mode, program the current to full scale rated value
(3 A)
†
and the voltage to the full scale rated value (8.0 V)
†
.
3 Divide the reading on the rms voltmeter by the load resistance to obtain rms
current. The readings should be within the limit of 4 mA.
4 Repeat steps (1) through (3) for the other output.
Common Mode Current Noise
The common mode current is that ac current component which exists between
the output or output lines and chassis ground. Common mode noise can be a
problem for very sensitive circuitry that is referenced to earth ground. When
a circuit is referenced to earth ground, a low level line-related ac current will
flow from the output terminals to earth ground. Any impedance to earth ground
will create a voltage drop equal to the output current flow multiplied by the
impedance.
1 Turn off the power supply and connect a 100 k
9
resistor (R
S
) and a 2200 pF
capacitor in parallel between the (-) terminal and chassis ground at the rear
output terminals.
2 Connect a digital voltmeter across R
S
.
3 Turn on the power supply. Select the output to be tested and the high voltage
range (20V/1.5A)
†
, enable the output, and set the display to the limit mode.
When the display is in the limit mode, program the output to the full scale rated
value (20 V and 1.5 A)
†
.
4 Record the voltage across R
S
and convert it to current by dividing by the
resistance (DVM reading/100 k
9
). Note that the current is less than 1.5
m
A.
5 Repeat steps (1) through (4) for the other output.
†
For E3646A model, and see
Table A-3
for other models.