GP-485 Datasheet, PDF (2/6 Pages) PerkinElmer Optoelectronics – Mini-Triggered Spark Gaps and Transformers

Miniature Triggered
Spark Gaps
The triggered spark gap is a three
element, gas-filled, ceramic-to-metal,
hermetically sealed, pressurized
switch that operates in an arc dis-
charge mode, conducting moderately
high peak currents for short dura-
tions. Commutation between two
main electrodes is initiated by a
trigger pulse.
Applications
Precision timing and firing for in-flight
functions such as rocket motor igni-
tion, warhead detonation and missile
stage separation. Each of these
applications involves the activation
of electro-explosive devices such as:
• Exploding bridgewire (EBW)
• Exploding foil initiator (EFI)
• Electronic safe and arm (ESA)
• Slapper/detonator
These compact small, rugged gaps
were designed for high-reliability
applications where size, switch
speed, and ability to withstand
rugged missile environmental condi-
tions of extreme shock, temperature,
and vibration are required. They are
designed for switching peak currents
up to 10kA at operating voltages
from 2.0 to 4.0 kV with reliable
triggering voltage of 2kV. Prefires
and failure to fire have been fully
evaluated in the basic gap designs.
Switching speeds of 70ns with trigger
pulse energies as low as 500 micro-
joules is typical.
Conduction
Current
Trigger
Voltage
Time
Turn-on
Time
Figure 2. Trigger Voltage Breakdown and
Main Gap Conduction Current
Performance
Characteristics
Electrical characteristics are
determined by testing in the circuit
shown in Figure 1. The output circuit
consisting of the switch, a 0.2 µF
capacitor, and a 0.25 ohm current
viewing resistor (CVR) is typical for life
testing. It closely matches the condi-
tions found in many typically used
circuits. For function testing, the 0.25
ohm CVR is replaced with a 0.005
ohm CVR.
Typical data taken with a 0.005 ohm
CVR are shown in Figure 2. This
curve contains traces of the trigger
voltage and conduction current. First,
the trigger voltage rises to the point
of trigger breakdown. Then there is a
period designated “turn-on” or delay
time during which the arc is forming
followed by main gap conduction.
This delay time varies from 50 to
1500 ns depending on gap operating
voltage, trigger mode, amplitude and
pulse width.
+ 1.0 mΩ
CT
VT(IN)
2N6798
OE
AE
+
GAP
T
5 mΩ
+
2.4-3.5 KV
0.2 µF
TR
CVR
—
VT(IN)
Volts DC
20-40
100-200
CT
µF
XFMR
2.2 TR-2189/2206
0.10 TR-2190/2207
Figure 1. Triggered Spark Gap Test Circuit
NORMAL
OPERATING
REGION
KNEE
VT(min)
CUTOFF
REGION
OPERATING
RANGE
SELF-BREAKDOWN
REGION
E-E(co) E-E(min)
E-E(max)
SBV
E-E = ELECTRODE-TO-ELECTRODE VOLTAGE
Figure 3. Transfer Characteristics
page 2
PerkinElmer Optoelectronics