Method for dispense verification

The present invention relates to a method for verifying dispense of a fluid from a dispense nozzle, the method comprising the steps of: providing a source of electromagnetic radiation and a receiver of the electromagnetic radiation from the source of electromagnetic radiation, such that the flow of a fluid from the nozzle passes through a path of electromagnetic radiation from the source to the receiver; energizing the source such that the source produces electromagnetic radiation; illuminating the receiver with the electromagnetic radiation; generating with the receiver a first signal; setting a threshold based on the first signal; dispensing fluid from the dispense nozzle; obstructing the electromagnetic signal between the source and the receiver with the fluid dispensed from the dispense nozzle; generating with the receiver a second signal; comparing the threshold and the second signal substantially continuously to indicate start of a dispense of fluid from the dispense nozzle; generating with the receiver a third signal; comparing the third signal and the threshold to indicate finish of a dispense of fluid from the dispense nozzle; determining a first time period between generation of the second signal and generation of the third signal; determining a second time period of an expected temporal duration between start and finish of the dispense of fluid from the dispense nozzle; and comparing the first time period and the second time period to verify the dispense of fluid from the dispense nozzle. .