The tester generates two different ” signals for checking a digital storage oscilloscope. The first is a stepped voltage on to which glitches are superimposed.
The second is a rectangular 2 kHz signal on to which a 15 Hz analog signal is superimposed The first signal quickly shows whether the oscilloscope eliminates the glitches during signal processing. If it does, the measurements cannot be fully trusted. It can also be used to check the trigger function; if this is poor, it will not be able to cope with the signal properly.
The second signal shows whether at a given setting low-frequency signals remain clearly visible (they should).
The stepped voltage is generated by oscillator IC1a and a digital-to-analog converter (DAC)—see diagram. Th ( converter consists of IC2. D1-D4, R3-R6, and R9. The signal is buffered by T1. Diode D5 compensates the forward bias of the base-emitter junction of T1. The spikes are introduced by C4.
The second signal is produced by switching T2 in rhythm with the 2 kHz signal and changing the collector voltage with the 15 Hz signal generated by oscillator IC1b.
The circuit needs a supply voltage of 9-15 V and draws a current of about 50 mA.