Hubert Zangl

Nonintrusive Monitoring of Slug Sequence and Flow Stability in Dense-Phase Pneumatic Conveying

This article presents three sensing methods developed for the nonintrusive monitoring of important flow parameters in dense-phase pneumatic conveying. With the optical measurement system, images of the flow are acquired and an image analysis is used to determine the sequence, length, and velocity of slugs for given materials and operating conditions. The conveying parameters of interest are also monitored with a capacitive sensor by means of exploiting electrical properties of the flowing media. The charge-based measurement system uses a field meter to determine the electric field strength caused by charged particles and provides information about the sequence and regularity of the moving slugs. The noninvasive principle of all three methods avoids concerns about particle contact effects (e.g., wear of the measurement equipment or interference with the flow). All three prototype sensors have been tested under slug flow conditions. A comparison of the three sensing methods against key requirements in pneumatic conveying reveals that capacitive sensing seems to be best suited for reliable flow determination in slug flow.

Passive Wireless Devices Using Extremely Low to High Frequency Load Modulation

Whereas passive wireless communication in the Ultra High Frequency (UHF) domain features long ranges of several meters in free space, systems utilizing lower frequencies in the ELF (Extremely Low Frequency) to HF (High Frequency) domain can be advantageous in environments with conductive materials or where large antennas are not prohibitive. Additionally, the operation range is well defined and can be practically restricted to several centimeters like in Near Field Communication (NFC) Standard ECMA-340 Near Field Communication Interface and Protocol (NFCIP-2) (2003), although this does not necessarily mean that communication is secure Hancke (2008). In this chapter we investigate passive wireless devices in the frequency range from almost DC to tens of Megahertz, i.e. from the ELF to the HF domain. Common abbreviations for the ITU frequency ranges are summarized in Table 1. The most common Radio Frequency Identification (RFID) systems use the LF (@125 kHz) and the HF (@13.56 MHz) bands. This chapter also considers lower frequencies.