Basic Test Technician Math

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What are some basic power supply electronic math formulas that a test technician should know?

120AC input - 1.141 = 118 VDC

The 1.141 is the full wave bridge rectifier

One of my managers use to use these other formulas but I'm not sure if they are correct or have to get them

How to get the DC power supply output voltage

He would take the AC output voltage X something i don't know

But he was solving to get the DC supply buss, how do you get it please?

example of that was 120 VAC output X something = 150 VDC power Buss


10X probe formula is what?

If you have a 20 volt peak to peak using a 10X probe what is the formula?

If you have 1 volt only the oscilloscope using a 10x probe , what is the voltage? what is the formula?
 

I think the equation you are trying to remember is VAC * 1.414 = VDC. The peak value of an AC waveform is the square root of 2 higher than the RMS value. An AC voltage is normally given as RMS for power distribution. Root 2 is 1.414 not 1.141. You multiply, not subtract.

If you want to take account of the diode drop it is typically 0.7V per diode so 1.4V for a bridge rectifier.

Modern oscilloscopes compensate for probe settings providing they are set up correctly. If you have an old one that doesn't correct for it then 5V shown with a 10x probe means the voltage is really 50V,

Keith
 

5V shown with a 10x probe means the voltage is really 50V
Click to expand...

Do you take the Peak voltage or Peak To Peak voltage and multiple it by 10X?
 

I am not sure I understand your question.

The probe shows one tenth of the voltage on the oscilloscope compared to the voltage that really exists. So, if you measure 5V peak on the oscilloscope then the voltage was really 50V peak. If you measure 5V peak to peak on the oscilloscope then the voltage is really 50V peak to peak.

Keith
 

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