Mass flow instruments, in fact all process instruments, experience wear from the conditions of the process in which they are installed. Temperature, electronic component tolerance shift, contamination build up over time (even very slight), plus other factors will all contribute to affecting the accuracy of an instrument.
Your instruments should regularly undergo, at a minimum, a calibration check if not a recalibration. But how often? Because the nature of each application is different (conditions, running time, etc.) a calibration can last three years or three months.
Bronkhorst® instruments do not have specified due dates for calibration. Bronkhorst® suggests that our instruments be calibrated every year. However based on the application conditions, and perhaps company quality procedures, each customer must determine when they need to send in an instrument for recalibration.
Properly calibrated instruments will be more accurate, more reliable, help ensure consistency, and help improve production yields.