Test Conditions
Direct current (DC) stabilized power supply with AC input voltage of 220V, full load output (regarding multi-output, all channels are fully loaded). AC input voltage can be set to 90V, 220V, or 265V according to requirements, and tested under full load output conditions. Test Method: During testing, set the oscilloscope's TIME/DIV to 10uS/div and bandwidth to 20MHz. The peak-to-peak voltage displayed on the oscilloscope is the output ripple voltage (including spikes, the peak-to-peak value is the sum of ripple and noise). 1) Adjust the input voltage of the DC stabilized power supply to the nominal voltage and set the output current to the rated current. 2) The ripple of the DC stabilized power supply is generally indicated by peak-to-peak value. Aeronautical power supply
Primary Test Method. The ripple and noise of a DC stabilized power supply are AC components superimposed on the DC output voltage. The measurement of ripple and noise is conducted under rated load and normal temperature. For switching type AC/DC DC stabilized power supplies, the output ripple voltage is a series of small pulses with high-frequency weight, thus the peak-to-peak value is generally measured rather than the root mean square (RMS). The measurement value is indicated in millivolts peak-to-peak (mVp-p). For example, if an AC/DC DC stabilized power supply has a ripple peak-to-peak of 50mV, its RMS value is low, only 5mV, but its applicability to a system must be further considered. Due to the high-frequency weight contained in the measured ripple, special measurement techniques are required to obtain accurate measurement results. To measure all the high-frequency harmonics in the ripple peak, a scope with a 20MHz bandwidth is generally used. Secondly, when conducting ripple measurements, it is necessary to be very careful to avoid introducing erroneous signals into the test equipment. When measuring, the probe ground clip must be removed as the ground clip can act like an antenna and absorb noise in a high-frequency radiation field, which can interfere with the measurement results. The measurement method using a probe with a ground loop to eliminate interference. This is a method of measuring the output ripple voltage of a DC stabilized power supply using a 50Ω coaxial cable. The coaxial cable is directly connected to the scope. To reduce noise, an aluminum or copper ground plane should be used during the measurement. The measurement value is half of the actual value. 36V Aircraft Power Supply
Utilizing a dual-line measurement method
Place the DC stabilized power supply above the grounding plate by 25mm, where the grounding plate is made of aluminum or copper. The common output terminal of the DC stabilized power supply and the AC input ground terminal are directly connected to the grounding plate. The grounding wire should be thick and not less than 50mm in length. Use a 300mm long twisted pair made of 16AWG copper wire, connecting one end to the power supply output and the other end in parallel with a 47μF tantalum capacitor, then connect it to the oscilloscope. The capacitor leads should be as short as possible, and pay attention to not reverse the polarity. The oscilloscope probe's "ground" should be connected as close as possible to the grounding loop. The oscilloscope bandwidth should not be less than 50MHz, and the oscilloscope itself should be grounded. Output noise tests (including peak-to-peak noise, telephone balance noise, wideband noise, and discrete noise). 400Hz power supply
