Abstract: A radio frequency identification (RFID) monitoring system (12) for monitoring a plurality of RFID tags, and in particular for monitoring a plurality of vials incorporating such tags and stored at a low temperature, (eg. ?80° C.) within a storage unit (10), for example a freezer. The RFID system (12) comprises an RFID reader (28) and at least one antenna (34a-34i) for transmitting and receiving RF signals to communicate with the RFID tags. The system (12) further includes an electronic switch (38), preferably a FET switch, interposed between the RFID reader and the at least one antenna (34a-34i) to connect a particular antenna (34a-34i) to the RFID reader (28) and transmit RF signals from the antenna (34a-34i) to the RFID tags. The switch (38) is controlled to intermittently connect the antenna (34a-34i) to the RFID reader (28) to regulate the power of the RF signal transmitted from the antenna (34a-34i). The system enables an RFID tag to operate at low temperatures.

Abstract: Corrosion is monitored by making a resistance measurement between a contact and an uncorroded or relatively uncorroded portion of the article to be monitored. Changes in the resistance measured are a result of the presence of a corrosion product, or the breakdown of protective coatings by corrosion. The contact may be a sensor washer which is held in place around a threaded stud 6 by nut 12. The washer comprises a steel ring 14 and an electrically conducting ring 18 which is insulated from ring 14 and contacted by circling 21 and conductor wire 23 in resin jacket 22. The measurement may be made on magnesium alloy gearboxes in helicopter. The alloy may be protected by a paint film so that the initial resistance measured is very high.