LP2800N logic probe — TTL, DTL and CMOS, pulse memory, 30ns detection

The LP2800N is a professional-grade logic probe designed for testing and troubleshooting TTL, DTL, and CMOS digital circuits. Unlike a basic voltmeter, it features a built-in pulse memory function that captures single-shot pulses and low-repetition-rate signals as narrow as 30ns — signals that are nearly impossible to detect even with a fast oscilloscope. Three colour-coded LEDs give instant visual feedback on logic state and pulse activity, making it an essential tool for any electronics workbench.

Key Specifications:

• Compatible logic families: TTL, DTL, CMOS
• Supply voltage: 4.5V – 18V DC (powered from the circuit under test)
• Input impedance: 1MΩ (typical)
• Minimum detectable pulse width: 30ns
• Maximum detectable pulse width: 500ms
• Logic HIGH threshold (TTL): >2.3V
• Logic LOW threshold (TTL): <0.8V
• Pulse memory: yes — latches single pulses for visual indication
• LED indicators: 3 × LEDs (Red = HIGH, Green = LOW, Yellow = Pulse)
• Pulse LED intensity: proportional to signal duty cycle
• Input protection: built-in overvoltage protection

LED Indicator Guide:

• Red LED ON: logic HIGH level detected
• Green LED ON: logic LOW level detected
• Both RED + GREEN ON: signal is at an intermediate/undefined level
• Yellow LED ON: pulse activity detected (brightness proportional to duty cycle)
• Yellow LED dim: low duty cycle or infrequent pulses
• Yellow LED bright: high duty cycle or continuous pulses
• Memory mode: yellow LED latches ON after a single pulse is detected

How to Use:

• Connect the power leads (red = VCC, black = GND) to the circuit under test
• Touch the probe tip to the test point
• Read the LED state: Red = HIGH, Green = LOW, Yellow = pulse activity
• For pulse memory: press the RESET button to clear the latched pulse indication
• Switch between TTL and CMOS mode using the logic family selector switch

Applications:

• Digital circuit debugging and fault finding
• Microcontroller and MCU I/O pin testing
• Single-pulse and one-shot circuit verification
• Clock signal presence and frequency checking
• PCB assembly and production testing
• Electronics education and lab work