Low voltage tester for e.g. vehicles - has CMOS comparator circuit for detecting voltage with LED indicator

摘要

The low voltage tester esp. for vehicles has in its shaft a display which can be connected to a current source, a test probe fixed to the shaft, and a contact potential. The tester indicates the pressure and polarity of voltages. The test voltage is measured using a CMOS comparator (6) to which it is input via a resistor. The polarity of the voltage is shown by light emitting diodes (4,5) driven by two output amplifiers (7,8) in the form of npn and pnp transistors. The input resistance is determined by the internal resistance of the human body. The measurement probe (2) is contained within a casing which moves within the shaft of the tester against the force of a spring.