Keithley 2790 User Manual

1-8 Model 2790 SourceMeter
®
Switch System User’s Manual
Bridgewire test
The air bag inflator has two terminals connected to a bridgewire, which is coated with a
primer that ignites when sufficient current passes through the wire. The bridgewire’s resis-
tance is typically from two to three ohms (2Ω being the most common). To avoid unintended
ignition, the level of test current applied is generally 50mA or less.
As shown in Figure 1-3, a fixed current is sourced through the bridgewire. The voltage
across the bridgewire is then measured by the DMM of the Model 2790.
Figure 1-3
Bridgewire testing
With the low ohms math function selected, the R
BRID
reading can be read directly from
the display of the Model 2790.
I-source readback — Before performing the bridgewire test, you can verify the actual
current flowing in the test circuit by using the I-source readback circuit.
NOTE A more accurate ohms reading can be achieved using the Ω4 function of the
Model 2790 (1mA fixed). See Section 6 for details.
2790
DMM
v
I SOURCE
Bridgewire
Under
Test
(RBRID)
RBRID =
V
MEAS
ISOUR
Keithley 2790 SourceMeter Switch System
Keithley
7751,7752,
or 7753
Module

Keithley 2790 Specifications

General

Brand	Keithley
Model	2790
Category	Switch
Language	English