SYSTEM FOR ALTERING A DATA DISTRIBUTION DISPLAY

1403390 Particle analysis systems COULTER ELECTRONICS Ltd. 27 Oct 1972 [4 Nov 1971] 49659/72 Heading G1N The invention relates to a Coulter type particle analysis system in which pulses in each amplitude/ size range pass through respective "window circuits" and are counted by accumulator (integrator) circuits. The integrator signals are cyclicly connected to a C.R.T. or plotter to provide a number-V- size distribution curve display. According to the invention a predetermined (zero shift), bias may be added to each integrator output to cancel noise signals or to make the display show deviation from a standard curve. As shown, Fig. 1 pulses from sensor 14 are applied to "windows" 16 feeding integrators 21. . 24 connected through switches 51. .54, (sequenced by clock 44) to a C.R.T. display 40. Positive/ negative bias from potentiometers 111. .114 is added to the integrator outputs through summing resistors 91. .94. A typical switch circuit using both series and shunt F.E.T.'s simultaneously is illustrated in Fig.3 (not shown). The bias may be used to improve particularly the leading edge of the display curve by offsetting the signal due to diluent only in the sensor. Alternatively The biases may be set to give zero deflection with a standard solution in the sensor (which will obviously give a mirror image distribution curve with zero signal from the sensor). Thus a standard mirror image signal may be set up from a reference curve superimposed on the screen.