Changing the Vertical Signal Gain

• When a signal is viewed on the CRO display the amplitude of the signal can be measured by counting the number of divisions that the signal "covers" on the display and multiplying by the scale of each division.
  • • i.e if the signal "covers" 4 divisions at 5 volts per division,
      the signal amplitude is 20 volts.
• Now because the signal being viewed can be a large range of sizes ( from a couple of millivolts up to 200 Volts ) we need to adjust the viewing scale on the display in order to achieve the optimum viewing size of the signal.
  • • i.e if we attempted to view a 10mV sine wave and a 30V sine wave on the same scale one or both of the signals would not be properly visible on the display.
      A graphical example of this.

How Do We Change The Vertical Gain?

• Well firstly we consider the diagram below which shows the Vertical Gain Control for each channel labelled with Volts/div.

• Now we know that each control has settings labelled from 5 millivolts per division to 20 Volts per division.
• The vertical gain is changed by simply rotating the control to the desired setting. Some graphical examples of this.

Things To Remember About The Vertical Gain Control.

1. If we are viewing two signals on the display, they can be viewed such that each signal is on a different vertical scale. So be aware of the setting of both vertical gain controls.
2. The red knob ( the Variable Vertical Gain Control ) that lies within the Vertical Gain Control must be rotated completely clockwise until a "click" is heard to ensure calibration and correct readings. (Be Warned - there will be turkeys who play around with these knobs just to ruin your results and get a laugh, so always be sure to check this. )

The Variable Vertical Gain Control

• This control as mentioned above is located in the centre of the Vertical Gain Control and is used to vary the signal gain ouside the limits of the Vertical Gain Control. It is most useful to check the general shape of a signal.

  

• ALWAYS be sure that this control is not left in the uncalibrated ( calibration relies on the knob being rotated completely clockwise until a "click" is heard ) position when making measurements of signal amplitude.

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Revised: Friday, 17 July 1998