IRMU - Initiator Resistance Measurement Unit
The IRMU is a highly accurate 4-wire Ohm Meter used to test the bridge wire in the NASA Standard Initiator (NSI). The NSI is used to initiate the detonation of an explosive bolt, shape charge, etc. The explosives are used for a variety of applications including: separating the solid rocket boosters from the main fuel tank on the shuttle, ejection seats, vehicle launch pad bolts, etc.
The IRMU uses a PC interface via a USB port to log data, perform self-diagnostic tests, calibrate the instrument, etc. Summit Products designed and manufactured the IRMU and coded a custom Windows based program to NASA specifications.