Oscilloscope Audit Procedure

 

This procedure outlines the steps in determining and documenting the current performance status of analog oscilloscopes.  An oscilloscope probe with a 10X option is required.

 

Plug the oscilloscope into AC power and turn it on.  It will typically take several seconds for the oscilloscope to warm-up, which allow the traces to be observed.  The oscilloscope, typically, has two channels.  Each channel will be tested.  The signal source for the test is the PROBE ADJUST output on the oscilloscope front panel.  This signal is a fixed square wave output of approximately 1 kHz and 0.5 vpp.  The probe might need adjustment for the waveform to optimally appear as a square wave.  The adjustment is a small inset screw on the oscilloscope end of the probe.  But first, a display or trace is required.

 

CH1 --

Locate the TRIGGER section of the front panel.  Assure that the TRIGGER MODE is set to AUTO and the SOURCE selection is CH1.  If a trace is not visible on the screen, press the BEAM FIND button and a bright beam should appear on the screen.  Whether the beam is on the upper or lower half of the screen indicates how the trace CH1 vertical POSITION is adjusted and how the CH1 vertical POSITION should be readjusted.

 

TRIGGER MODE settings

            MODE – AUTO

            SOURCE – CH1

HOLDOFF – MIN if so equipped

VERTICLE MODE settings for CH1:

            MODE – CH1

            VOLTS/DIV – outer concentric knob at 0.1 volts for 10X probe

                                     inner concentric knob (CAL) fully clockwise

            COUPLING – AC

HORIZONTAL MODE settings for CH1:

            SEC/DIV – outer concentric knob at 0.2mS/div

                                inner concentric knob (CAL) fully clockwise

                                no DLY or MAG

 

Now, connect the probe to the PROBE ADJUST signal on the front panel.  You should now see a square waveform displayed.  If not, assure that the HOLDOFF is at MIN.  You may have to adjust the TRIGGER LEVEL to see a steady waveform. 

 

The vertical deflection should be about 5 major divisions (0.5V) and the period should be about 5 major divisions (1mS).  Adjust the vertical and horizontal position controls to optimize the waveform position for measurement.  Determine and document the waveform vertical amplitude to a resolution of 0.01V.  Determine and document the waveform period to a resolution of 0.02mS.

 

CH2 –

Repeat the CH1 process for CH2, replacing CH2 for every CH1 in the instructions.  Document the results.