electrode l 104 although varying bias voltages can be applied if desired the application of a bias voltage difference between the electrodes 102 and 104 causes an ionic current to flow in the fluid 114 resistors ra 120 and rb 122 represent the electrical resistance of the fluid in the constriction 108 and the fluidic resistor 110 respectively the sensing electrode 106 is capacitively coupled to the fluid through the electric double layer capacitance cdl 124 the circuit elements ra 120 rb 122 and cdl 124 are measureable directly the output voltage vout 126 is measured as the output from sensing electrode 106 the ionic current between electrodes 102 and 104 creates voltage drops across the constriction 108 in the fluid channel and the fluid resistor 110 which typically presents an approximately equal fluidic electrical resistance but has a larger volume the sensing electrode 106 is embedded in the fluid between the constriction 108 and the fluid resistor 110 when a particle enters the constriction 108 it alters the ionic electrical current and because of the voltage division between the two fluidic resistances changes the electrical potential of the sensing electrode 106 the time varying nature of the particle passage through the constriction makes the electrical potential at the sensing electrode 106 time varying as well which allows this signal to be electrically coupled through the electrical double layer capacitance cdl 124 the signal 126 can be amplified with an operational amplifier or other type of amplifier as desired to properly measure the output voltage 126.