Signal stability is a metric which is calculated over the normalization beads that are spiked into every mass cytometry sample. It is defined as the correlation between Time and each of the bead channels. The CyTOF instrument has a known issue where signal intensity diminishes over time. Fluidigm's software has a normalization algorithm that fixes this trend using the beads. However, sometimes the operator might forget to run the normalization tool or the tool cannot fix the trend. The signal stability will raise an alert in such situations.