By making a mini tester, for several years I use them when repairing household electrical and radio engineering. Assembled by the classical scheme, the device allows with a sufficient accuracy for practice to measure the voltage to 300 V in DC and AC, test resistors, diodes, transistors, and capacitors.
For the manufacture of the mini-tester requires a small number of electronic components, and none of them ie rather expensive and short supply does not apply. They are always what is called a hand, you can find them in stock at any radio Amateur. And as a supporting structure, the mounting plate and the body of the instrument is used… the measuring head M42100 (or similar type) for DC voltage measurement 3 or 30 V.