Circuit Testing
Saturday, 21 July 2018
6:49 PM
Analyse the circuit before applying power to ensure that you know what to expect.

Double check all connections, especially power supply connections, before applying power. 

Apply power to the IC before applying the signals.

Measure voltages with respect to circuit “common”. If you need the difference in potential between two points, measure each with respect to earth and then subtract. The common terminal of some instruments (particularly the oscilloscope) may be tied to earth and would short out some part of your circuit. Or it may inject noise into a sensitive portion of your circuit.

When using the oscilloscope to measure voltages, be aware that the accuracy of an oscilloscope, as a voltmeter, is of the order of 3%.

To measure voltages accurately (better than 0.5% accuracy) use the Digital Multimeter. When measuring AC voltages with the Digital Multimeter, make sure that the frequency of the signal you are measuring is within the limits specified for your Digital Multimeter.

Measure current by determining the voltage across a known resistor. Then calculate the current. Ammeters are rarely sensitive enough, tend to load the circuit, and often inject noise into sensitive nodes.

Remove the signal from the IC before removing the power. 

Change components and connections with the power off. 