GB1434244A - Apparatus for pulse method measurement of dispersion values of particles - Google Patents

Abstract

1434244 Pulse width discriminator KOMBINAT MEDIZIN - UND - LABORTECHNIK VEB 22 June 1973 [23 June 1972] 29895/73 Heading H3P [Also in Division G1] In apparatus for the pulse method of measurement of dispersion values of particles dispersed in a suspension comprising a transducer having a measuring opening arranged to provide electrical output pulses related to the dispersion values of the particles dispersed in the suspension in response to the passage of the particles through the opening and a circuit arrangement for evaluating the pulses derived from the transducer, the circuit arrangement either reduces the areas of derived pulses relating to particles flowing through the measuring opening adjacent the perimeter of the measuring opening or suppresses the derived pulses to exclude them from the formation of a measuring value, the derived pulses relating to all other particles flowing through the measuring opening passing unvaried through the circuit arrangement. The circuit arrangement comprises a gate 1, Fig. 1 for the derived pulses, a multivibrator 3 controlling the gate 1 and a differentiating element 2 responsive to the derived pulses and arranged to trip the multivibrator 3. In Fig. 1 the differentiating element 2 produces a pulse (Fig. 2, not shown) from the leading edge of an input pulse so as to trigger a monostable multivibrator 3 into its unstable state. The monostable multivibrator 3 opens the gate 1 for the duration of its unstable period so as to completely pass input pulses of width less than or equal to this unstable period. Input pulses of greater width are shortened. In a further embodiment Fig. 3, a differentiating element 2 produces positive and negative going pulses (Fig. 4, not shown) from the leading and trailing edges of the input pulses. The positive pulse triggers a monostable multivibrator 4 into its unstable state, and the negative pulse is passed via a NOT or inverter element to provide a positive input to an AND element 6. Provided the input pulse width is less than or equal to the unstable period of the multivibrator 4 the AND element produces an output to operate a bi-stable multivibrator 7 which opens the gate 1 so as to allow the input pulse delayed in a delay circuit 8 to pass to the output. The bi-stable multivibrator 7 is reset by a negative pulse obtained from a differentiating element 9 corresponding to the trailing edge of the delayed pulse from 8. Input pulses of width greater than the unstable state period of the multivibator 4 do not energize the AND element 6 so that the gate 1 remains closed and no output is obtained.