In summary, both passive and active probes have strengths and weaknesses. Understanding which probe type to use in an application is very important, such as an active probe would be the proper choice when dealing with high frequencies. A passive probe would be more appropriate when dealing at lower frequencies and with higher voltages. Printed circuit board designs are becoming more complex and the ability to probe a particular type of circuit is critical. The scope user must be able to deal with IC legs, vias, and surface mount devices (SMD). There are several ways to allow a single ended scope to make differential measurements. One method is to float the scope, a bad choice and should not be attempted. Other, more acceptable methods would be to use two single ended probes and then do the math, use isolators, or the most desirable method is to use true differential probes. In actual application, differential amplifiers are not ideal and some of the common mode signal always passes through to the output. The measure of how well a differential amplifier rejects this common signal is called the common mode rejection ratio. There are several types of current measurement methods that can be used with the oscilloscope. DC to high frequency AC can measure using shunts. AC current transformers, and AC current probes can be used. Hall effect devices are useable on DC to low frequency AC. A general purpose combination transformer and Hall Effect device which can measure DC to high frequency AC is the standard current probe type supplied.