Device for detecting leading end of pipette tip, and storage medium storing program for detecting leading end of pipette tip
A pipette tip leading end detection device for detecting that a leading end of a pipette tip is close to a reference surface set to a reaction vessel includes a pipette nozzle, pump, nozzle driver, pressure sensor that detects a pressure generated between the pipette tip and pump, and hardware processor. The hardware processor obtains a determination value using an AD conversion value obtained from the pressure while the pipette nozzle is being lowered, and detects that the leading end of the pipette tip is close to the reference surface on the basis that the determination value is a threshold value or more. The determination value is a calculation value indicating a pressure change speed calculated from AD conversion values within a past certain time and the threshold value is a value larger than maximum noise.
1. A pipette tip leading end detection device for detecting that a leading end of a pipette tip attached to a pipette nozzle and sucking or discharging liquid is close to a reference surface set to a reaction vessel having an accommodation part capable of accommodating the liquid, comprising:
the pipette nozzle with the pipette tip attached thereto;
a pump connected to the pipette nozzle;
a nozzle driver that moves the pipette nozzle up and down,
a pressure sensor that detects a pipette tip-pump pressure generated between the pipette tip and the pump; and
a hardware processor that controls operations of at least the pump and the nozzle driver, wherein
the hardware processor:
obtains a determination value using an AD conversion value which is a value obtained by A/D converting the pipette tip-pump pressure detected by the pressure sensor while the pipette nozzle is being lowered towards a bottom surface of the accommodation part by the nozzle driver and air is being discharged or sucked from the leading end of the pipette tip by the pump; and
detects that the leading end of the pipette tip is close to but not in contact with the bottom surface of the accommodation part as the reference surface on the basis that the obtained determination value is equal to or greater than a preset threshold value, wherein:
the determination value is a calculation value indicating speed of a change in the pressure calculated by using a plurality of AD conversion values within a past certain time including a latest AD conversion value among AD conversion values of the pipette tip-pump pressure detected every certain time or consecutively; and
the threshold value is a value larger than a maximum value of noise included in the determination value which occurs in the course of moving the leading end of the pipette tip towards the bottom surface of the accommodation part.
2. A non-transitory computer readable storage medium storing a pipette tip leading end detection program for causing a computer to detect a leading end of a pipette tip close to a reference surface, causing the computer to:
detect a pipette tip-pump pressure generated between a pump connected with a pipette nozzle and the pipette tip by a pressure sensor while the pipette nozzle with the pipette tip sucking or discharging liquid attached thereto is being lowered towards a bottom surface of an accommodation part of a reaction vessel having the accommodation part capable of accommodating the liquid and air is being discharged from the leading end of the pipette tip, and obtain a determination value using an AD conversion value which is a value obtained by A/D converting the detected pipette tip-pump pressure; and
detect that the leading end of the pipette tip is close to the bottom surface of the accommodation part as the reference surface on the basis that the obtained determination value is equal to or greater than a preset threshold value, wherein:
the determination value is a calculation value indicating speed of a change in the pressure calculated by using a plurality of AD conversion values within a past certain time including a latest AD conversion value among AD conversion values of the pipette tip-pump pressure detected every certain time or consecutively; and
the threshold value is a value larger than a maximum value of noise included in the determination value which occurs in the course of moving the leading end of the pipette tip towards the bottom surface of the accommodation part.