Scientific 5000 Series, Руководство пользователя

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APPENDIX M
13-62
Version 1.23
MODEL 5000 SERIES MANUAL
I
BO
Test
I
BO
is run in two parts. First the V
BO
is found and then the voltage is ramped slowly
starting at just below the V
BO
while both the current and voltages are monitored (a
load resistor is in series with the device).
I
BO
is the current measured just at the peak voltage. Some variation will inevitably
occur between successive readings of devices that exhibit a flat characteristic. For a
sharp breakover device, the current recorded will be that value just prior to
breakback.
The maximum possible current is 1 mA (typically I
BO
is less than 200
μA).
V
BB
test
V
BB
is the measured voltage across the device at a specified current (typically 100
μA). A 250K resistor is used in series with the device to stabilize the device (sharp
breakback devices have a tendency to oscillate).
I
H
, V
T
Tests
These tests are run in a manner similar to the I
H
and V
T
tests in an SSOVP device
(see Appendix H for complete descriptions). The I
H
test differs from the SSOVP test
in that the applied current begins at 250 mA and is reduced in 1 mA steps until the
device drops out (it is a single test measure method).
V
S
Test
V
S
is the device voltage just prior to the device firing on. Current is applied at 80% of
the measured I
S
value (the minimum allowable current is 2.5mA). The resulting
measured voltage is V
S
.
I
S
Test
I
S
is the current at which the device fires on. This current is determined by
successively increasing the applied current until the device fires on.
R
S
Test
The R
S
measurement of a Sidac device is derived from four other parameters (V
BO
,
I
BO
, I
S
and V
S
) and is calculated as follows:

R
S
= (V
BO
-V
S
) / (I
S
-I
BO
)

R
S
allowable range is 50
– 500 ohms, within this range, I
S
is limited to a
minimum of 2.5mA.
See Figure 13-46 for Sidac characteristic. All parameters can be measured in both
polarities.
Note that for most devices with R
S
within this range, the I
S
current will be greater than
10mA. Below this range, I
S
can oscillate on some devices. This condition normally
poses no problem in determining that R
S
is greater than the maximum limit (500
ohms). At I
S
equal to 10mA, the delta V (V
BO
-V
S
) would be less than 5 volts for the