A syringe (10; 30; 40), comprising: a plunger having a shaft extending longitudinally between a proximal end and a distal end, the shaft including a first section and a second section ; a barrel having a proximal end and a distal end and a cylindrical sidewall extending longitudinally between the proximal and distal ends, the sidewall defining an internal volume, the distal end of the plunger being inserted into a proximal end of the barrel and being movable within the internal volume with respect to the barrel in the longitudinal direction; a first probe and a second probe ; and a microcontroller disposed on the barrel and in electrical communication with the first and second probes , the microcontroller being configured to: (i) measure a capacitance between the first and second probes , the measured capacitance having a first capacitance value when the first section of the plunger shaft is between the first and second probes and a second capacitance value different from the first capacitance value when the second section of the plunger shaft is between the first and second probes , and (ii) determine that an injection has been completed when the second capacitance value is measured, the syringe (10; 30; 40) being characterized in that the first section of the shaft has a first diameter, the second section of the shaft has a second diameter different from the first diameter, the second section being disposed between the first section and the proximal end of the plunger , and the first and second probe are disposed on the barrel adjacent a proximal end of the barrel , the first and second probes being opposite to one another such that the interior volume of the barrel is radially between the first and second probes . a plunger having a shaft extending longitudinally between a proximal end and a distal end, the shaft including a first section and a second section ; a barrel having a proximal end and a distal end and a cylindrical sidewall extending longitudinally between the proximal and distal ends, the sidewall defining an internal volume, the distal end of the plunger being inserted into a proximal end of the barrel and being movable within the internal volume with respect to the barrel in the longitudinal direction; a first probe and a second probe ; and a microcontroller disposed on the barrel and in electrical communication with the first and second probes , the microcontroller being configured to: (i) measure a capacitance between the first and second probes , the measured capacitance having a first capacitance value when the first section of the plunger shaft is between the first and second probes and a second capacitance value different from the first capacitance value when the second section of the plunger shaft is between the first and second probes , and (ii) determine that an injection has been completed when the second capacitance value is measured, (i) measure a capacitance between the first and second probes , the measured capacitance having a first capacitance value when the first section of the plunger shaft is between the first and second probes and a second capacitance value different from the first capacitance value when the second section of the plunger shaft is between the first and second probes , and (ii) determine that an injection has been completed when the second capacitance value is measured, the syringe (10; 30; 40) being characterized in that the first section of the shaft has a first diameter, the second section of the shaft has a second diameter different from the first diameter, the second section being disposed between the first section and the proximal end of the plunger , and the first and second probe are disposed on the barrel adjacent a proximal end of the barrel , the first and second probes being opposite to one another such that the interior volume of the barrel is radially between the first and second probes . <EOS>