GxT Ferret 54 ENGINE DIAGNOSTIC CENTER - Manual (Page 53)

LOGIC TRACE SCOPE
Use the logic trace to observe regular or intermittent pulses on wires for accessories, sensors,
lamps, solenoids, slow computer codes, or other on/off electrical signals. Press NEXT to adjust
the scan rate. Press SELECT to set the threshold between -20 and +20 volts DC. Press
RECORD to freeze and display a copy of a particular trace. The copy can then be viewed
without motion, separate from the live display.
Scan Rate 8Û
Threshold 5.00V~ Aux 4.30Volt
The logic trace scope displays a line trace, showing voltage transitions through a specified
threshold. The actual voltages are displayed in the upper right hand corner of the display. The
threshold must be set to a voltage that is within the range of voltage change for transitions to
appear, otherwise a straight line trace will show.
SOLENOID DUTY CYCLE
Use Solenoid Duty Cycle to measure mixture controlled carburetors, or frequency output
sensors such as some pressure and air flow sensors. Also use this test to check Hall-effect
switches.
SOLENOID DUTY CYCLE 52% ~ 28 to 31
Frequency 10 Hz 50 100
%£££££££££££££££££££££ %
839 RPM Battery 14.10 Volt
The term “Duty Cycle” means the portion of time that the signal is switched to ground,
which is when power is applied to solenoids, etc. Duty cycle should be constant within
a few %, and is usually about 50%.
Hz for some sensors will vary directly with RPM. MC solenoid frequency should be constant,
around 8-10 Hz.
SELECT changes the scaling of the “DUTY” reading for either:
milliSeconds mS
Percent %
degrees / 60
°
The upper right reading shows the longest and shortest duty. If the numbers match, the duty
is steady. If there is a difference, the signal pulse width is varying which may mean that there
is active control (closed loop), or if it should not vary it could be a defective signal source or
connection.
4-24