VOLTCRAFT VC 820-1 Notice D'emploi page 28

Normally, the resistance of the measuring lines is so low (ca. 0.1 to 0.2 ohms)
that it can be neglected. However, this low resistance can even result in inac-
curate values within the 400 ohm measuring range.
Therefore, use the REL function to avoid the indication of the resistance of the
measuring lines.
For a resistance >1MΩ the electronic system needs a little bit of time to sta-
bilise the indication.
Testing diodes and checking the acoustic continuity
Proceed as follows to test diodes and semiconductor paths or to check the acoustic
continuity of voltage-free lines / fuses:
a) The measurement set-up (connection of the measuring lines) corresponds to the
one of the resistance measurement. Press the blue second-function button once.
Now, the measuring instrument switches from resistance measurement to diode
test, the „
b) „.0L" for overload is indicated for open or not connected measuring lines or for
high-resistance (or interrupted) semiconductor paths. Connect the measuring
prods to the voltage-free semiconductor component, a diode or a transistor. When
doing this make sure that the red measuring line is connected to the anode and the
black measuring line to the cathode. Now, the forward direction is tested. If the p-
n-junction functions properly, a value of between 0.45 and 0.75VDC will be dis-
played for Si-diode paths and a value of between 0.2 and 0.4VDC will be shown for
Ge-diode paths. But if „.0L" appears instead of a voltage value, the diode path is
interrupted or the measuring lines have been mixed up. If a voltage higher than 1V
is measured for transistors it is possibly a transistor with integrated resistors.
The reverse direction of a diode path is tested by connecting the cathode with the
red measuring line and the anode with the black measuring line. If a voltage value
is displayed now, the diode is defect. But if „.0L" is indicated, it is a high-resis-
tance diode path (OK).
red measuring
line
rote
Meßleitung
c) To switch to the acoustic continuity check, activate the blue second-function
switch top right of the rotary switch once more. Above the „ohm symbol" the sym-
bol for the acoustic continuity check is displayed. Connect the measuring prod to
the absolutely voltage-free object to be measured (lines, cables, circuits etc.). An
audio signal is generated for resistance values below approximately 70 ohm. The
loudest signal is generated for „0" ohm.
28
" symbol becomes visible on the right side of the display.
black measu-
ring line
Meßleitung
load, switch
Durchlaßrichtung
red measuring
line
schwarze
rote
Meßleitung
black mea-
suring line
schwarze
Meßleitung
reverse direction
Sperrichtung