Part 2 of R&S NGP814 Power Supply - Review


It is important for any power supply to be able to maintain the output level independant of the load variation.

The NGP814 load regulation test is shown below.


Channel 1 @32V, 6.25A:


A- Using the built in multimeter in the DL3021

= [(31.9943V - 31.8313V) / (31.8313V) ] x 100% = 0.5120746%


B- Using DMM6500

= [ (32.00127V - 32.00333V) / (32.00333V) ] x 100% = - 0.00643683%

The negative value indicates a leading power factor (Capacitive load).

Figure below shows the behaviour at the moment of switching on the load.

@no load: Vripple P-P = 0.8 mV

@Full load: Vripple P-P = 0.82 mV (Corrected)



Channel 3 @64V, 3.125A:


A- Using the built in multimeter in the DL3021

= [(63.9909V - 63.9102V) / (63.9102V) ] x 100% = 0.126271%



B- Using DMM6500

= [ (64.00465V - 64.00836V) / (64.00836V) ] x 100% = - 0.00579612%

Same as channel 1 the negative value indicate a leading power factor.

Channel 3 also shows a dip in voltage at the moment of switching.

@no load: Vripple P-P = 1.6 mV

@Full load: Vripple P-P = 1.8 mV (Corrected)



It can be noticed that the built-in multimeter of the electronic load and the external multimeter have quiet a noticeable difference in the measured values.

Assuming that the dedicated DMM6500 is the more accurate of the two it shows a load regulation of about -0.006% which is an impressive value achieved by the NGP814.


One thing to notice about transient behaviour is the yellow circle in both graphs, that is the reading at the moment of switching on the load where the power supply jumps from No-Load to Full-Load.

This voltage dip is still tolerable, 2.5mV for the 32V range about 5mV for the 64V range, which shows that this voltage dip is proportional to the voltage of the test. The red circle still needs more investigation as it took about 12 seconds for the voltage to reach the accurate steady state.