While taking an oscilloscope measurement, remember these key fundamentals:

1. Turn the oscilloscope on, which can take a significant amount of time. For example, some oscilloscopes can take 30 minutes or more to reach specified accuracy.
2. Before taking a measurement, understand the measurement being attempted. What are the conditions and what channels are being used?
   1. Identify the conditions to measure, such as V_IN, V_OUT, loading, and so forth.
   2. Add labels to the channels on the oscilloscope to help with simple identification of each channel. Users are most likely showing the waveforms collected to other users, and making a habit out of labeling the waveforms on each channel helps others understand the information.
3. Connect the LDO terminals to each oscilloscope channel as desired. Setting the channels to high impedance termination mode (1MΩ) is a good starting point - unless the signal to be measured is also terminated with a 50 ohm termination, high impedance mode is appropriate. Determine whether AC coupling or DC coupling is appropriate for each channel - is the signal to be measured a 10mV AC signal superimposed on a 10V DC signal? If so, the 10mV signal can be difficult to view with DC coupling, and AC coupling is appropriate in this case. Choose probes that are matched to the oscilloscope's bandwidth for transient measurements. Verify that each oscilloscope channel shows the correct voltage and current levels in accordance to what levels are being set with the LDO.
   1. Choosing an oscilloscope probe for a measurement can be a difficult task, so, when choosing an oscilloscope probe, choose the correct probe for the correct measurement. Refer to Choosing an Oscilloscope Probe for additional information on choosing an oscilloscope probe.
   2. Be cautious when connecting a probe with long wires. Long return paths from the probe tip back and through the ground clip back to the probe can pick up additional noise, which affects measurement readings. Refer to Implications of Parasitics to learn more about the affects of parasitics in a circuit.
4. Once the oscilloscope is turned on, the previously configured oscilloscope conditions for the horizontal system time scale and the vertical system voltage scale show on the screen. Adjust the horizontal time scale (seconds/div) to zoom in or zoom out on the time scale.
   1. Adjusting the horizontal time scale zooms in or zooms out of a waveform, which helps to show the full waveform around the desired signal activity. For example, if users are measuring the impulse response of a control loop that has approximately 100kHz bandwidth, then setting the time scale to 10μs/div is a good starting point. For an example of incorrect oscilloscope scaling, refer to Visualization.
   2. Consulting the oscilloscope's user guide can help make setup adjustments to align with the measurement.
5. Determine the signal that makes the most sense to trigger the oscilloscope capture. For LDOs, it's often the case that the signal that triggers the transient behavior of interest is the rising or falling edge of the enable (EN) signal, or perhaps a change in the load current. When the triggering signal has been determined, go to the trigger settings in the oscilloscope and select the channel corresponding to the trigger signal. Then, set the trigger to detect the edge of the signal (this can be a rising or falling edge, depending on the test being performed) at a voltage or current level that is roughly halfway between the minimum and maximum values. For example, if the EN signal rises from 0V to 2V, set the trigger to detect the rising edge on the channel corresponding to the EN waveform when the voltage crosses 1V.
6. Once the oscilloscope is configured and triggered, is the desired measurement reached?
   1. If the desired measurement was not reached, then continue to adjust the vertical and horizontal scale, configure the Volts/div and the offset of each channel.
      1. Additionally, check for signal path compensation. If DC measurement accuracy is required, then running a self calibration is recommended. Oscilloscope manufacturers have recommendations for how often to perform a self calibration.
   2. Users can get more use of the screen space by implementing a horizontal delay (shifting the waveforms to the left, for example) instead of the triggering event capturing in the middle of the screen.
7. Refer to the oscilloscope user's guide for examples of taking a proper measurement.
   1. Additional resources are also available on the oscilloscope manufacturer's website. For example, if using a Teledyne Lecroy oscilloscope, refer to Hands-On Guide to LeCroy Color Digital Oscilloscopes.