Abstract: A metal detector (10) which uses a metallic test sphere (5) to pass with the product through the detector head (2) at periodic intervals. The frequency generator (21) which generates the signal sent to the oscillator coil (11) is capable of operating on numerous frequencies in the 50 kHz to 2 MHz range. The product is passed through the detector head (2), with and without the sphere (5) present, for each of the operating frequencies. The detected signal from the product and the product with metal is characterized for each of the operating frequencies. In this manner the frequency which produces the highest ratio of product with metal present signal to product signal without metal present can be identified. A second version of the metal detector (40) uses a frequency synthesizer (43) which may be rapidly scanned through a range of frequencies while the product is passing through the detector head (41).

Abstract: A metal detector (1) having an oscillator coil (10) which radiates an electromagnetic field in the vicinity of an article to be tested. The field is detected by a primary set of receiver coils (15) which are in close proximity to the oscillator coil (10), as well as by a secondary set of receiver coils (18) located relatively more distant from the oscillator coil. Moving or vibrating metal external to the detector cavity (7) surrounded by the coils (15, 18) will produce a modulated waveform (48) in the primary coils (15) which is similar in period to the modulated waveform (56) produced by the secondary coils (18), while metal passing through the detector cavity (7) will produce a waveform (24) from the primary coils (15) which has a period which differs from the period of the waveform (31) produced by the secondary coils (18).

Abstract: An impact flowmeter (10) for measuring a stream of free flowing bulk solids (60) having low mass flow rates. The flowmeter (10) includes a barrier (18) between the flowing stream of solids (60) and the sensor chamber (16). A primary sensing element (48) includes an impact plate (50) positioned to lie in flow chamber (14). A velocity sensor (39) is mounted to an inlet chute (32) for providing a velocity output signal (284) in response to the velocity of the solids in the stream of solids (60) as the stream of solids (60) passes the velocity sensor (39). The velocity sensor (39) includes a velocity circuit (278), a first capacitance sensor (41) and a second capacitance sensor (43) mounted to the side wall of the inlet chute (32) and arranged so that the solids in the stream of solids (60) pass by the first capacitance sensor (41) before passing by the second capacitance sensor (43).