6
3.3
Low Frequency CMRR Adjustment
a.
Referring to Fig. 10, connect output BNC to an oscilloscope has good grounding.
b.
Connect both input lines to a 220/200 VAC, 60/50 Hz power source.
c.
Put SW1 at 1/100
.
d.
Set the VOLTS/DIV switch on oscilloscope’s panel to 1 mV and the TIME/DIV switch to
5ms. Then a 60/50 Hz sinusoid waveform should be displayed on the screen.
e.
Adjust VR1 to make the amplitude of displayed waveform as small as possible.
Finally the amplitude should be less than 1.5 mVp-p (after excluding noise).
Fig. 10
3.4
Repeat 3.2 and 3.3 adjustment until both adjustments are O.K.