GB1388096A - Non-diluting particle counter - Google Patents

Abstract

1388096 Particle analysis systems COULTER ELECTRONICS Ltd 2 Aug 1973 [10 Aug 1972] 36853/73 Heading G1N In a Coulter-type particle analysis system, of the kind wherein the sample liquid is ejected into the electrolyte in front of the measuring aperture, the ejector operates by thermal expansion. The SAMPLE EJECTOR, 28, Fig. 1, comprises a hollow container 30 with a small aperture (such a sub-standard measuring wafer 36) in one wall. The expansion device 34 comprises an electricresistance-heater (46) in a body of e.g. silver or beryllium oxide. In a practical construction Fig. 5, the ejector may be built into the nozzle 131 of a syringe having a plunger 138 to suck-in the sample ready for ejection by the thermal expander 134. The plunger may be held in its upper position by a detent 162 engaging a spring latch 164. In this position it closes the back-end of the nozzlepart. In an alternative form Figs. 9, 10, (not shown), the bore 147 may extend right through the plunger so that the ejector may be loaded through the aperture 176 at the back. The ejector-plunger-housing may have an arm to engage a mounting block attached to the aperture tube, Fig. 8 (not shown). HEATER CONTROL CIRCUIT. To supply a controlled amount of energy to the thermal expansion device so that a precise amount of sample is ejected, the heater may be energized by discharge of a capacitor Fig. 3. Aternatively Fig. 4 the heater 46 may be energized from a constant voltage source 72 over the "start" contacts 80 of relay 82, and the current monitored by the drop across series resistor 94 applied to integrating amplifier 102. The integrator output is compared at 110 with a reference value from source 112 to control "stop" relay 70. When the start relay 82 drops out, resistor 116 is connected across-the integrator capacitor 104 to discharge it.