Digital Voltage/ Current Display

This V/I display module is eminently suitable for building into an existing DC power supply, where it gives a precise indication of the set voltage or the current consumption of the load. The circuit diagram appears in Fig. 1. The 3-digit readout is based on A/D converter Type CA3162 and BCD-to-7 segment decoder Type CA3161, both from RCA. The common anode connections of LED displays LD1-LD3 are successively con- nected to the positive supply line via T, T3. Provision has been made to sel- ect the correct position of the decimal point. In the voltage range, the decimal point lights on LD3, and the resolution is therefore 100 mV. Two current ranges are possible: 0-9.99 A (link a) or 0-0.999 (.999) A (link b). The current sensing resistor is therefore either OR1 or 1R0- see Fig. 2. It is important that R6 does not affect the output volt- age of the supply in question. It must, therefore, be fitted ahead of the voltage divider that con- trols the output voltage. DPDT switch Si sele...