A function generator is connected to an analog oscilloscope. I can see a sine wave. Can I read DC voltage with the help of DC offset knob? If so, can the minimum DC voltage be negative?

  • \$\begingroup\$ is this a school assignment? \$\endgroup\$ – jsotola Jan 21 at 3:34
  • \$\begingroup\$ The DC offset knob on what machine? \$\endgroup\$ – DKNguyen Jan 21 at 4:33
  • \$\begingroup\$ If the input is DC coupled, you can measure the DC voltage of a signal. The Zero Volt reference level can usually be positioned vertically anywhere on the screen (and even off the screen!) \$\endgroup\$ – Peter Bennett Jan 21 at 4:34

You can short circuit the input to ground, this gives you a straight line at 0 V. You can position this with the offset knob at a position you like - this will be your zero volt position.

Now you can switch the input from ground to a DC coupled input. You will see your waveform, the AC as well as the DC. The DC content is the offset of the middle of your curve to the before positioned zero line.

See the red dashed line in this picture: Suppose you configured this as your zero line. Than the distance assigned with the arrow is your DC offset.

enter image description here

  • \$\begingroup\$ A good illustration of the thesis that circuit ground is a relative concept... \$\endgroup\$ – Circuit fantasist Jan 21 at 7:50
  • \$\begingroup\$ I'm not sure what you are refering to. \$\endgroup\$ – jusaca Jan 21 at 7:52
  • \$\begingroup\$ Just a thought inserted... What we see on the scope screen is a geometric representation of invisible voltages. We can vertically move the zero line (ground) and set it in any desired position... and then measure the deflection of the beam relative to this position... So the ground vertical position can be arbitrary chosen. \$\endgroup\$ – Circuit fantasist Jan 21 at 9:04

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