The LP-535 Logic Probe Kit tests different types of digital logic circuit families.
Working Voltage
4 - 16VDC
Current Consumption
Max 5mA @ 5V
Max 15mA @ 15V
Frequency Response
Over 50MHz
Minimum Detectable
Pulse Width
10nsec
Input Impedance
1M
Ω
Input Overload Protection
70V AC/DC (10s)
Supply Voltage Protection
50V AC/DC (10s)
Operation Temperature
0
O
C to 50
O
C
Switch
Selectable Audio Indicator HI Level
CIRCUIT DESCRIPTION
SPECIFICATIONS
-3-
INPUT
LED STATES
SOUND
SIGNAL
LO
HIGH
PULSE
Probe not connected to power.
*
Interpreting
the LEDs
LED On
LED Off
LED Blinking
No Sound
Sound
*
*
Logic tip is not connected or Logic “0” no
pulse activity.
Logic “1” no pulse activity.
Logic “0” with positive single pulses.
Logic “1” with negative single pulses.
Logic “0” with positive continuous pulses.
Logic “1” with negative continuous pulses.
This information for switch to the sound position.
The Elenco Model LP-535 Logic Probe Kit is a
convenient and precise instrument for use in the
measurement of logic circuits. It displays logic levels
(high or low), sounds high level, and voltage
transients down to 10 nanoseconds. To detect the
high and low logic levels, the LP-535 uses two
inverters, U1A and U1B (see the Schematic
Diagram). One inverter drives the LO (green) LED
and the other, the HI (red) LED.
The red LED lights when the input voltage is more
than 50% of the supply voltage. The function of the
switch for TTL or CMOS levels input signal makes up
the special circuit on the base of transistors from U2
and additional components. The outputs of U1A and
U1B are connected to differential circuits C3/R3 and
C4/R7.
These differential circuits select signals,
when the test signals are the pulses.
After the
differential circuits, the short pulses go through
inverters U1C and U1D to the yellow LED. This LED
blinks when the detecting diode D4 opens. At this
time, capacitor C6 discharges. The lit time of the
yellow LED depends upon the value of C6. The LP-
535 is equipped with a sound circuit. When the input
signal is HI, the oscillator (U1E, U1F) is started and
the frequency through switch S1 passes to the
speaker.
