A system or instrument comprising: a sequencing cell (150, 200, 300) that includes a nanopore, the nanopore configured to receive a tag that is connected to a nucleotide, thereby creating a threading event; - a signal generator configured to apply an alternating signal across the nanopore of the sequencing cell (150, 200, 300), each cycle of the alternating signal comprising a first portion and a second portion, wherein voltage levels of the second portion are opposite of a reference voltage than voltage levels of the first portion; - an analog-to-digital converter configured to acquire a first set of voltage data during the first portion of a plurality of cycles of the alternating signal, wherein each data point of the first set of voltage data corresponds to a value of a resistance of the nanopore at a different time, where the resistance of the nanopore changes when the tag is received within the nanopore; characterized in that it further comprises - a digital processor configured to: ∘ determine a time-shifted set of voltage data (710, 720) from the first set of voltage data, wherein each cycle of data points of the first set of voltage data and the time-shifted set of voltage data (710, 720) includes a specified number of data points; ∘ compute difference data by computing differences between data points of the first set of voltage data and corresponding data points of the time-shifted set of voltage data (710, 720); and ∘ identify the threading event based on one or more data points in the difference data. - a signal generator configured to apply an alternating signal across the nanopore of the sequencing cell (150, 200, 300), each cycle of the alternating signal comprising a first portion and a second portion, wherein voltage levels of the second portion are opposite of a reference voltage than voltage levels of the first portion; - an analog-to-digital converter configured to acquire a first set of voltage data during the first portion of a plurality of cycles of the alternating signal, wherein each data point of the first set of voltage data corresponds to a value of a resistance of the nanopore at a different time, where the resistance of the nanopore changes when the tag is received within the nanopore; characterized in that it further comprises - a digital processor configured to: ∘ determine a time-shifted set of voltage data (710, 720) from the first set of voltage data, wherein each cycle of data points of the first set of voltage data and the time-shifted set of voltage data (710, 720) includes a specified number of data points; ∘ compute difference data by computing differences between data points of the first set of voltage data and corresponding data points of the time-shifted set of voltage data (710, 720); and ∘ identify the threading event based on one or more data points in the difference data. ∘ determine a time-shifted set of voltage data (710, 720) from the first set of voltage data, wherein each cycle of data points of the first set of voltage data and the time-shifted set of voltage data (710, 720) includes a specified number of data points; ∘ compute difference data by computing differences between data points of the first set of voltage data and corresponding data points of the time-shifted set of voltage data (710, 720); and ∘ identify the threading event based on one or more data points in the difference data.