Logic probe
Encyclopedia
A logic probe is a hand-held pen-like test probe
used for analyzing and troubleshooting the logical states (Boolean
0 or 1) of a digital circuit. While most are powered by the circuit under test, some devices use batteries. They can be used on either TTL (transistor-transistor logic) or CMOS
(complementary metallic oxide semiconductor) integrated circuit devices.
There are usually three differently-colored LED
s on the probe's body:
The pulse-detecting electronics usually has a pulse-stretcher circuit so that even very short pulses become visible on the amber LED. A control on the logic probe allows either the capture and storage of a single event or continuous running.
When the logic probe is either connected to an invalid logic level (a fault condition or a tri-stated output) or not connected at all, none of the LEDs lights up.
Another control on the logic probe allow selection of either TTL or CMOS family logic. This is required as these families have different thresholds for VIH and VIL.
Some logic probes have a separate audible tone for each of the logical states. An oscillating signal causes the probe to alternate between high-state and low-state tones.
A logic probe is a cheap, versatile and convenient digital test instrument, but can test only a single signal at a time. When many logic levels need to be observed or recorded simultaneously, a logic analyzer
is used.
Test probe
A test probe is a physical device used to connect electronic test equipment to the device under test . They range from very simple, rugged devices to complex probes that are sophisticated, expensive, and fragile.- Voltage probes :Voltage probes are intended to measure voltages on the DUT...
used for analyzing and troubleshooting the logical states (Boolean
Boolean logic
Boolean algebra is a logical calculus of truth values, developed by George Boole in the 1840s. It resembles the algebra of real numbers, but with the numeric operations of multiplication xy, addition x + y, and negation −x replaced by the respective logical operations of...
0 or 1) of a digital circuit. While most are powered by the circuit under test, some devices use batteries. They can be used on either TTL (transistor-transistor logic) or CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
(complementary metallic oxide semiconductor) integrated circuit devices.
There are usually three differently-colored LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s on the probe's body:
- Red and green LEDs indicate high and low states respectively
- An amber LED indicates a pulse (as used in a NOID Light to test for pulses to fuel injectors on a electronically controlled fuel injection vehicle)
The pulse-detecting electronics usually has a pulse-stretcher circuit so that even very short pulses become visible on the amber LED. A control on the logic probe allows either the capture and storage of a single event or continuous running.
Another control on the logic probe allow selection of either TTL or CMOS family logic. This is required as these families have different thresholds for VIH and VIL.
Some logic probes have a separate audible tone for each of the logical states. An oscillating signal causes the probe to alternate between high-state and low-state tones.
A logic probe is a cheap, versatile and convenient digital test instrument, but can test only a single signal at a time. When many logic levels need to be observed or recorded simultaneously, a logic analyzer
Logic analyzer
A logic analyzer is an electronic instrument which displays signals in a digital circuit. A logic analyzer may convert the captured data into timing diagrams, protocol decodes, state machine traces, assembly language, or correlate assembly with source-level software.Presently, there are three...
is used.