Electrical resistance test device with an attached comparison resistance set

A megohm tester comprising:

• a housing;
• a comparison set;
• two probes for contacting preselected test sites and sensing resistance therein;
• oscillator means for receiving said sensed resistance from said probes and generating output pulses and an output pulse period proportionate to said resistance;
• transducer means for receiving said output pulses from said oscillator means and converting said output pulses into an audible and visual signal;
• a low voltage power source operatively connected to each of said probes, said oscillator means and said transducer means to facilitate the sensing of said output pulse generation and said audible and visual signal output thereof;
• said housing having a body portion and a cover portion, said body portion containing said oscillator, said transducer means and said power source having an exit means defined therein for passing said probes therefrom and means for affixing said comparison set to said cover of said housing;
• said probes having a first insulated probe wire having a first and second end, and a second insulated probe wire having a first and second end, a first elongated conductor having a proximal and a distal end, said distal end providing a contact area for engaging preselected test sites, said proximal end being soldered to said first end of said first insulated probe wire, a first insulating cover circumscribing a portion of said first elongated conductor and permitting said distal end to protrude therefrom, a second elongated conductor having a proximal and a distal end, said distal end providing a contact area for engaging preselected test sites, said proximal end being soldered to said first end of said second insulated probe wire, and a second insulating cover circumscribing a portion of said second elongated conductor to permit said distal end to protrude therefrom;
• said power source comprising:
• a low voltage battery having a positive and a negative terminal;
• said relaxation oscillator means having a first transistor having an emitter lead, a base lead and a collector lead, a second transistor having an emitter lead, a base lead and a collector lead, a first resistor having a first and a second lead, a capacitor having a first and a second lead, a diode having anode and cathode leads, a light emitting diode having anode and cathode leads, and a second resistor having a first and a second lead;
• said transducer means having a speaker having first and second leads, said positive battery terminal being connected respectively to said second end of said first insulated probe wire and said emitter lead of said first transistor;
• said base of said first transistor being connected to said collector lead of said second transistor;
• said collector of said first transistor being connected respectively to said first lead of said capacitor, said cathode lead of said diode, said anode lead of said light emitting diode, and said first lead of said speaker;
• said second lead of said capacitor being connected to said first lead of said first resistor;
• said negative battery terminal being connected respectively to said emitter lead of said second transistor and said anode lead of said diode, said cathode lead of said light emitting diode, and said second lead of said speaker;
• said second lead of said first resistor being connected to said base lead of said second transistor and said first lead of said second resistor;
• said second lead of said second resistor being connected to said second end of said second insulated probe wire;
• said comparison set comprising ten 10 megohm resistors serially connected and comparison detection points which provide known combinations of resistance values of 10 megohms, 20 megohms, 30 megohms, 40 megohms, 50 megohms, 60 megohms, 70 megohms, 80 megohms, 90 megohms and 100 megohms.