Oscilloscope Basics: Cal Out and Aux Out

Fig. 1: Cal Out and Aux Out 
provide many useful outputs.

Oscilloscopes are generally thought of in terms of the signals that are input to them, but even oscilloscopes that are not equipped with function/signal generators can usually output some useful test signals.

Nearly all oscilloscopes have a Cal Out (calibration output) terminal on the front. Most Teledyne LeCroy oscilloscopes also have an Aux Out (auxiliary output) connector on either the front or back, depending on  model. Both outputs provide configurable signals that can assist you to compensate probes and attenuators, test frequency response, trigger waveform acquisition and coordinate multiple test instruments.

Oscilloscope Basics: External, Line and Fast Edge "Triggers"

An oscilloscope trigger synchronizes the oscilloscope timebase to the input signal so that the displayed trace is stable. In digital storage oscilloscopes, while the digitizer runs continuously converting analog voltage/current inputs to digital values, it is the trigger event that defines the “acquisition window,” marking the point where data is stored to acquisition memory, locking the signal data for display, measurement and further processing. 

Figure 1: The trigger setup showing the possible choices for the trigger source.

Triggers are set to fire based on the state of a trigger source waveform. What are commonly known as External, Line and Fast Edge "triggers" are not really different trigger types, per se, but alternative trigger sources.  Figure 1 shows the typical setup options for an Edge trigger, the most commonly used trigger type.  With Edge triggering, the oscilloscope is triggered when the source waveform crosses a user-defined threshold level and slope.  Usually, the source will be analog input channel C1-Cn. However, three other sources can be used to initiate an Edge trigger: an Ext(ernal) input, the Line (mains) power and, on some oscilloscopes, the built-in Fast Edge signal.