Velleman DCA55 - Manual (Page 9)

Atlas DCA User Guide October 2007 – Rev 7
Page 9
LEDs
An LED is really just a another type of diode, however, the
Atlas DCA
will determine that an LED or LED network has
been detected if the measured forward voltage drop is larger
than 1.5V. This also enables the Atlas DCA to intelligently
identify bicolour LEDs, both two-terminal and three-terminal varieties.
Like the diode analysis, the pinout, the
forward voltage drop and the associated
test current is displayed.
Here, the Cathode (-ve) LED terminal is
connected to the Green test clip and the
Anode (+ve) LED terminal is connected
to the Blue test clip.
In this example, a simple green LED
yields a forward voltage drop of 1.92V.
The test current is dependant on the
forward voltage drop of the LED, here
the test current is measured as 3.28mA.
Some blue LEDs (and their cousins, white LEDs) require high
forward voltages and may not be detected by the Atlas DCA.
LED or diode
junction(s)
RED GREEN BLUE
Cath Anod
Forward voltage
Vf=1.92V
Test current
If=3.28mA