Patent ID: 7126325
Filing Date: 2006-10-24
Classification: G01F,G01R

Abstract:
1. A digital multi-meter, comprising a switch for voltage/Ohm, a switch for mA/uA testing, a switch for large current testing, and connecting jacks for said switches, wherein, further comprising a circuit for indicating inserted jack and warning wrong insertion, said circuit comprising: a microprocessor control unit (MCU), including pins for connecting said switches and said jacks; three LEDs for indicating voltage/Ohm testing function, mA/uA testing function and large current testing function, when a function switch has been closed and the associated test jack has not been plugged in, said MCU signals the associated control pin to light up the LED beside the correct testing function jack therefore indicating to the user the correct jack to be used, when a function switch has been closed and the associated test jack has been plugged in, said MCU signals the associated control pin to shut off the LED therefore indicating to the user the correct jack has been inserted for testing, when a function switch has been closed and an incorrect test jack has been plugged in, the MCU signals the associated control pin to activate the LED to flash therefore warning the user an incorrect operation has been performed; sound device connecting to a pin of said MCU, said pin being turn on and off under the control of said MCU, when a function switch has been closed and an incorrect test jack has been plugged in, said MCU signals said pin to activate said sound device thus warning the user that an incorrect operation has been performed; wherein under any single fault condition including that one of the LED or sound device malfunctions, the circuit still warns the user that an incorrect operation has been performed.