Component Signiture Analysis

Hey All

I have a component signiture Analsist machine at work and when measuring a capacitor it displays a circle like signiture.

Depending on frequency it can turn into an oval shape. Although I have been explained on why the signiture is a circle like signiture, I don't fully believe it's the true explaination.

I have done research on the internet and it demonstrates how the signiture is a circle for capacitance but doesn't ever give a reason or explaination.

Can anyone here help.

Jason.

Are you sure that it is not just an oscilloscope connected in X Y display mode showing phase shift. As in the first line of pictures on this web page. This type of display is called a Lissajous pattern. A circle is produced when the phase shift is 90 degrees. With 50 Hz (Mains frequency) if you connect a capacitor and resistor in series and the capacitor has the same value of reactance as the value of the resistor then a circle is displayed with the Y axis showing the voltage across the resistor and the X axis showing the voltage across the capacitor. (0.1 uF and a 33K resistor will do this at 50 Hz)

Les.

Have a look at this link.

**broken link removed**

This isn't the tool I have but it shows an example of the signitures

Jason

In Fig 1 of your diagram you can see that the resistor R1 is in series with the device under test. (A capacitor in your case.) The Y axis is dispaying the voltage across the resistor and the X axis is displaying the voltage across the device under test. As you change the frequency the reactance of the capacitor (1/ (2πfC) will change causing the phase shift to change which will cange the circle into an ellipse

Les.**broken link removed**