A logic probe is a useful tool if you are working with logic circuits. Following
diagram - Fig. 1, shows a simple logic probe with a CMOS 4001 circuit.
The connection operates at the usual voltages for the CMOS 4000 series.
Fig. 1
Logic probes can be created in a variety of ways. Fig. 2 shows another logic probe
connection composed of transistors and one XOR gate. This probe indicates
logic states TTL - LOW, TTL - HIGH and indefinite state "Z".
Fig. 2
In both cases, it is absolutely necessary to pay attention to the correct power supply
of logic probes, adhere to the principles of correctness grounding. Only then will
the probe show the correct values of the logic levels.
