I designed and built this piece of instrumentation in response to the need for increased accuracy in a certain manufacturing process. The original power supply used a pair of large analog meters for voltage and current. Although these meters were fine for the supply's original intended use, their accuracy was no longer sufficient for the new application the supply was now being used for.
The unit was designed around a pair of off the shelf Simpson digital meters. A 200 V DC meter was used in conjunction with a 100:1 voltage divider to directly display 0-19,999 volts. A matching 200 mA DC meter was rescaled to directly read out 0-19,999 microamps. Since the unit was to be used in a production environment, it was essential that the meters read out in actual units and not require any operator interpretation or scaling of test results.
The voltage divider was assembled on a perf board. Pico fuses were included to limit maximum current drawn from the supply to 60 mA. This serves to protect the supply as well as the current meter shunt in case of operator error in connecting the unit to the device under test. A pair of high voltage BNC connectors were mounted on an isolated block on the rear panel. An internally mounted 10 turn potentiometer was used to provide for calibration. Click here for a schematic of the high voltage divider & meter.
