2
-
45. Beta is determined by setting the fixture switch
to BETA, and observing the display. Mentally shift the
decimal point three places to the right and read beta
directly. For example, a display reading of 0.127
indicates a dc current gain (beta) of 127.
NOTE
Beta is a temperature sensitive parameter.
Therefore, repeatable readings can only be
obtained by allowing the transistor to
stabilize at the ambient
temperature while
being tested. Avoid touching the transistor's
case with your fingers.
2
-
46.
Leakage
Tester
2
-
47. The 200 US conductance range effectively
extends the resistance measurement capability of the
8020A (up to 10,000 Ma) to the point where it can be
used to provide useful leakage measurements on passive
components. For example, you can detect leaky
capacitors, diodes, cables, connectors, printed circuit
boards (pcb's), etc. In all cases the test voltage is <5V
dc.
2
-
48. RESISTIVE COMPONENTS
2
-
49.
Leakage testing on purely resistive components
such as cables and pcb's is straight forward. Select the 200
nS range, install the test leads in the V/KR and
COMMON input terminals, connect the leads to the
desired test points on the unit
-
under
-
test, and read
leakage conductance. If an overrange occurs, select the
resistance range that provides an on
-
scale reading.
NOTE
Under high humidity conditions
(>80%)
conductance measurements may be in error.
T
O
ensure accurate measurements connect
clean test leads to the
8020A
and (with the
leads open) read the residual leakage in
nanosiemens. Correct subsequent
measurements by subtracting this residual
from the readings. (Finger prints or other
contamination on the pcb may also cause
residual conductance readings).
2
-
50. DIODES
2
-
51.
Diode leakage
(In)
tests require that the diode
junctlon be reversed biased when being measured. This
is accomplished by connecting the diode's anode to the
COMMON input terminal and its cathode to the
V/KR
input terminal. Leakage can then be read in terms of
conductance. In the event of an overrange, select a
resistance range that provides an on
-
scale reading.
2
-
52. CAPACITORS
2
-
53. Capacitor leakage measurements are easily
accomplished using the following procedure.
a.
Disconnect the capacitor from its circuit.
b.
Discharge the capacitor using a
lOOR resistor.
C
. If the capacitor is polarity sensitive (electro-
lytic, etc.), identify the positive side and connect
it to the
8020A's V/kR input. Connect the
negative side to COMMON. Non
-
polarized
capacitors can be connected either way.
d. Select the
200n range and allow the capacitor
to assume a charge (charge time is about 5
seconds or 10 seconds/ 100
IF, whichever is
greater).
e.
Select the 200
nS range and allow the reading to
stabilize. This may take a while for larger
capacitors. However, devices below 1
pF
stabilize rapidly.
f. Read the leakage in terms of conductance.
Overrange readings indicate a short or excessive
leakage.
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