A pyrotechnic device (UUT) is automatically tested for thermal response cacteristics using an automatically balanced
Wheatstone bridge. One branch of the bridge is a series of relay connected resistances which are selectively connected to
coursely balance the bridge using a voltage developed across the UUT. An FET in series with the series of resistances, in
response to the bridge null currents, finely balances the bridge. A low constant current pulse is used to generate a voltage
across the UUT and to balance the bridge. A second high constant current pulse is used to measure the transient thermal
response of the UUT. The transient test current pulses are generated automatically or manually and whose amplitude and
repetition rate are manually set. The pulses are generated by a D/A converter whose output is fed to a constant current
generator coupled to a manually settable resistance range for setting the value of the high current transient test pulse amplitude.
The lower value initial balance current pulse is separately settable by internal calibration switches and straps. The entire test is
less than 40 ms.
R.H. Peterson; K.S. Pickens