| CPC A01G 7/06 (2013.01) [G05D 16/2066 (2013.01); H02P 25/06 (2013.01)] | 27 Claims |

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1. An apparatus for injecting liquid into a plant comprising:
a variable volume dosing chamber with a plunger disposed within the chamber and a chamber inlet and outlet, the inlet and outlet in fluid communication with a common volume of the chamber, wherein the plunger translates in a linear direction relative to the chamber along a common longitudinal axis;
a power source;
a motor configured to drive translation movement of a piston via a threaded shaft causing a change in volume in the chamber and liquid to be alternatively received and discharged from the chamber;
a trigger;
a processor in communication with the power source, the motor, and the trigger, the processor being configured to:
control voltage to the motor, and to control power to the motor by creating a pulse force comprising a plurality of pulses of power that provide energy to said motor;
identify a change in pressure of the liquid discharged from the outlet during an injection operation by monitoring the motor current or the number of revolutions of the motor;
vary the pulse force in response to the identified change in pressure to control the pressure of the liquid discharged from the outlet during an injection operation; and
wherein the processor uses the motor current or the number of revolutions of the motor to look up gain to be applied to a pulse force parameter selected from off time, pulse time, voltage and current, in stored data, and wherein the gain is applied to a selected pulse force parameter by the processor, to vary the pulse force.
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