8-Channel Voltage Display

Simultaneously monitoring the trends of 8 slowly varying voltages is normally very diffi- cult, if not impossible, even with the aid of 8 analogue or digital voltmeters. This circuit turns a common oscilloscope into a versatile 8-channel display for direct voltages. The trend of each of the 8 input levels is readily observed, albeit that the attainable resolution is not very high. The circuit diagram shows the use of an 8-channel analogue multiplexer, IC1, which is the electronic version of an 8-way rotary switch with contacts X0- X7 and pole Y. The relevant 8-CHANNEL VOLTAGE DISPLAY channel is selected by applying an binary code to the A-B-C inputs. Example: binary code 011 (A-B-C) enables channel 7 (X6 -Y). The A-B-C inputs of IC, are driven from three suc- cessive outputs of binary counter IC2, which is set to oscillate at about 50 kHz with the aid of Pi. As the counter is not reset, the binary state of out- puts Q5, Q6 and Q7 steps from 0 to 7 in a cyclic manner. Each of the...