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Bourns
Model 4030 Surge Protector Test Set
®
Theory of
Operation
6
The tester employs a linear voltage ramp generator, a low energy
capacitive discharge and a current limiting element, a precise 1 mA
current detection and control circuit, and a peak-hold reading metering
system. When 1 mA is conducted, the control circuit de-energizes the
power supply but maintains the clamping/breakdown voltage reading on
the meter as long as the test button is depressed.
When testing solid-state devices such as metal oxide varistors (MOVs),
silicon avalanche diodes, Zener diodes and thyristor devices, the ramp
voltage will increase until an exact 1 mA current is conducted through
the device under test. At this 1 mA current, the detector immediately
activates the control circuits which removes the voltage source in less
than 50 µs, latches the voltage peak-reading circuit, and displays the
peak voltage on the meter. (After the tester has latched, it is normal for
the reading to fluctuate ±1 V.)
It should be noted that the current available from the tester is generally
not enough to fully transition GDT and thyristor components and
devices into the low voltage state. GDT based devices will show the DC
Breakdown Voltage (DCBD) and for P-type thyristors, the breakover
voltage V
(the highest voltage occurring across the thyristor) occurs
BO
at the device's Zener voltage V
V
of P-type protectors. For N-type thyristor devices, V
BO
than V
. Therefore, the tester will produce only V
Z
The tester senses current flow through the test device and at 1 mA, the
control circuits are activated as described above. Two different voltage
ramps can be selected by the user: 200 V/s or 1000 V/s. The selector
jumper for this function is located within the tester enclosure. For
laboratory testing, QA approvals and precise measurements of Gas
Discharge Tubes (GDTs), the 200 V/s should be used. (GDTs can be
sensitive to 1000 V/s dv/dt after surge duty with low voltage GDTs.) For
high-speed bulk testing, sorting and incoming goods inspection, the
1000 V/s setting is practical. The tester has been factory set to 200 V/s.
. Therefore, the tester will measure actual
Z
measurements.
Z
is higher
BO
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