Inline heater overheating system and method

An inline heating system comprising:

• an inline heater including a heater element;
• a voltage source or a current source positioned to apply a voltage or a current to power the inline heater
• a memory configured to store a calibration data table that relates calibrated heater element resistances of the inline heater to at least one of fluid flowrates through the inline heater or input voltages or input currents to the inline heater;
• and
• an analog heater protection circuit configured to:
• (i) measure at least one of a current or a voltage at the heater element due to the applied voltage or the applied current,
• (ii) determine a heater element resistance (Re) of the inline heater using the applied voltage or the applied current and the measured at least one of the current or the voltage,
• (iii) compare the determined heater element resistance (Re) of the inline heater with a commanded fluid flowrate and a power setting of the heater element to the calibration data table to determine whether a no flow or low flow condition is detected, and
• (iv) (iv) stop a power signal or disable an enable signal when the heater element resistance of the inline heater indicates the no flow or low flow condition.

An inline heating system comprising:

• an inline heater including a heater element;
• a control unit configured to:
• compare a determined heater element resistance (Re) of the inline heater with a commanded fluid flowrate and a power setting of the inline heater to a calibration data table to determine whether a no flow or low flow condition is detected, and stop applying a current or a voltage to power the inline heater upon detection of the no flow or low flow condition;
• and
• a meter arranged to measure at least one of a current or a voltage at the heater element due to the applied voltage or the applied current, the meter outputting the at least one of the current or the voltage to the control unit to enable the control unit to calibrate the determined resistance to the outputted at least one of the current or voltage.