Keysight E3632A, Service Manual

Page: 34 / 73

1 Calibration Procedures
36 Keysight E3632A Service Guide
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 impendance to earth ground will
create a voltage drop equal to the output current flow multiplied by the
impendance.
1 Turn off the power supply and connect a 100 K Ω resistor (R
S
) and a 2200 pF
capacitor in parallel between the (–) terminal and chassis ground.
2 Connect a digital voltmeter (DVM) across R
S
.
3 Turn on the power supply. Select the 15 V/7 A range, 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 rated value (15.0 V and 7.0 A).
4 Record the voltage across R
S
and convert it to current by dividing by the
resistance (DVM reading/100 K Ω ). Note that the current is less than 1.5 μ A.