Explosives trace detectors are used by public safety organizations to screen packages, vehicles, luggage and other items for minute residues of explosives left on them by people who have recently handled explosives. Instrument users wipe the surface of the item to be screened with a swab and insert the swab into the instrument. Analysis results are produced in less than a minute and often in less than ten seconds. Desktop-sized ETDs are used at fixed checkpoints where their relatively large size, weight, and need to operate on alternating current power can be accommodated. Alternatively, handheld ETDs used for screening activities that are mobile in nature require an easily-carried instrument that can operate on battery power.