8 Service and Maintenance
228 E364xA User’s and Service Guide
Common Mode Current Noise
The common mode current is the 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
Ω
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 (DVM) across R
S
.
3 Turn on the power supply. Select the output to be tested and the high voltage
range (20 V/1.5 A)
[1]
, enable the output, and set the display to the limit mode.
When the display is in the limit mode, program the voltage to the maximum
programmable value and the current to the full rated value (20.6 V
[2]
and 1.5
A
[1]
).
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 µA.
5 Repeat step 1 through step 4 for the other output.
[1] For the E3646A model. For other models, refer to Table 8-5.
[2] For the E3646A model. For other models, refer to Table 7-3.
To Next Page
Loading...
Need help?
General
