Wayne Kerr AP10030, User & Service Manual

Page: 35 / 70

Wayne Kerr AP 1kW Power Supplies • Issue 2 35
Displays & Metering
Current and voltage monitoring is by digital displays and bargraphs. Voltages
proportional to output current and voltage are fed to the meter circuits via analogue
switches IC18, IC20 and IC25 and buffer amplifiers IC19-B and IC24-C. The analogue
switches switch the voltage derived from the output voltage and current (when the enable
switch is on), or the output voltage and current settings (when the enable switch is off).
The voltmeter circuit consists of IC1 and display driver IC2 (front panel circuit diagram).
The ammeter circuit uses IC5 and driver IC6 (front panel circuit diagram). The input to
the common bargraph comparator array, IC8 and IC9 (front panel circuit diagram), is
switched between the current and voltage inputs at 100Hz, as are the voltage and current
bargraph displays. This is accomplished by the oscillator of IC7-3 (front panel circuit
diagram) and the analogue switches of IC4.