Techniques for measuring sequences of nucleic acids are provided. Time-based measurements (e.g., forming a histogram) particular to a given sequencing cell can be used to generate a tailored model. The model can include probability functions, each corresponding to different states (e.g., different states of a nanopore). Such probability functions can be fit to a histogram of measurements obtained for that cell. The probability functions can be updated over a sequencing run of the nucleic acid so that drifts in physical properties of the sequencing cell can be compensated. A hidden Markov model can use such probability functions as emission probabilities for determining the most likely nucleotide states over time. For sequencing cells involving a polymerase, a 2-state classification between bound and unbound states of the polymerase can be performed. The bound regions can be further analyzed by a second classifier to distinguish between states corresponding to different bound nucleotides.