GB1482791A - Pulse amplitude discriminating circuit - Google Patents

Abstract

1482791 Particle analyzers COULTER ELECTRONICS Ltd 11 Oct 1974 [16 Oct 1973] 44133/74 Heading G1N [Also in Division H3] A pulse discriminator in a Coulter particle analyzer, accepts pulses within upper and lower threshold levels and outputs rectangular pulses of uniform duration, with an amplitude corresponding to the input. The circuit is useful for distinguishing platelets from red blood cells (which give larger pulses). PROCESSING ACCEPTABLE PULSES. The pulse from scanner 10 passes electronic-input-switch 16 and is applied to the lower and upper level comparators 20, 22, and a sample/hold circuit. As the pulse passes trailing-edge-detector 30 triggers univibrator 32 to open switch 42 passing the "heldvalue" to the analyzer circuit 44. While a value is held, output 64, from the sampler 24, operates bi-stable 54 to switch off the input at 16. Resetting. When the output-switching-pulse from univibrator 32 ceases trailing-edge-detector 46 provides a resetting pulse (i) on line 48, to bi-stable 54 to switch on the input at 16 to receive the next pulse (ii) on line 49 to clear the holding circuit (iii) on line 51 to reset bi-stable 38 if necessary. REJECTING LARGE PULSES. If the scanner pulse is of sufficient amplitude to pass the upper level comparator 22 (in addition to the lower level 20), it triggers bi-stable 38 to inhibit and gate 36 so that switch 42 is not operated by the univibrator 32. The circuit is then reset as before.