Microvolt probe


Posted on Dec 27, 2012

The current tracer helps locate a defective IC that is loading down the power supply. The tracer amplifies the small voltage drop caused by current flow along a fraction of an inch of PC wiring and drives an ordinary microammeter. Needle-point test probes are used to contatt the edge of a PC trace and to follow the current to determine which branch the current takes. One-half of a dual 741 op amp forms a dc amplifier with ac feedback to prevent oscillations and hum-pickup problems.


Microvolt probe
Click here to download the full size of the above Circuit.

It drives a 50-to-100 µ meter. The other op amp provides a center tap for the 9 V battery supply and zero adjustment with R4. Two diodes protect the meter. Resistor Rl eliminates the necessity for shorting the probes when the meter is zeroed. The value of 1 ohm is large when compared with the resistance of the meter leads plus the bridged portion of PC wiring.





Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Laser Beam Alarm
Motion-detection Digital Camera circuit
DC variable speed motor control
Low-cost-voltage-to-frequency-converter
autonomous car
RS 422 Compatible Indicator
Simple Electrification Unit
Bruces TPU Theory and Experiments
Automatic Switch Project 2
Electronic Ballast circuit diagram



Top