volt-ammeter for power supplies

9-40 — elektor september 1981 volt/ammeter for power supplies P. Gabler Without electricity there is very little you can do in electronics, therefore, a good quality power supply occupies a very important place in any reader"s set of priorities. It should have a wide adjustable voltage range providing a current of at least one or two amps. In addition, it would be a considerable advantage if the power supply were to include a built-in meter to display the output voltage and current levels. The ideal meter is a DVM which combines great accuracy with an easy-to-read display. The idea certainly makes sense. After all, plenty of stable power supplies have appeared in Elektor"s pages and so have several digital voltmeters. So the smallest range a DVM can have is some- where around 1 or 2 V. Right, now let"s get back to the measuring current. Figure 2 gives a view of the output section in the power supply including the power transistor T and the resistors connected to the output. R1 a...