Dual-Path Storage Oscilloscope

The dual-path storage oscilloscope is a device fitted with two independent analog inputs, a two-channel AD converter, a two-channel monitor, two input memories and one output memory, and a DA converter with an integrated analog filter. 

For differentiation, the signal is first immediately stored in channel 1. Then the same signal is stored in channel 2 and shifted one or more millimeters (or AA). When both spectra are then subtracted from each other, the result is the first derivative, which can be plotted digitally or, after DA conversion, recorded with an analog system (see [42] and Fig. 3-5). 

For higher-order differentiation, we used the following technique [42]  

With the help of an additional digital memory, is stored and then sent back twice with a difference of AA to the storage oscilloscope. After substraction one obtains the second derivative. This process can be repeated if higher-order derivatives are desired. 

In that case, after each newly generated derivative, the noise must be eliminated with a digital low-pass filter (Fig. 3-43). 

---