Heater element having targeted decreasing temperature resistance characteristics

A heater comprising:

• at least one resistive heating element comprising a material having a non-monotonic resistivity vs. temperature profile with a local maximum, a local minimum, and exhibiting a negative dR/dT characteristic over a predetermined operating temperature range along the non-monotonic resistivity vs. temperature profile;
• and
• multiple heater layers having a first layer and a second layer, wherein the first layer defines a plurality of zones of temperature control and the second layer defines fewer zones of temperature control with respect to the first layer, and wherein the second layer includes a higher heat generation per unit of surface area than the first layer and at least one negative dR/dT resistive heating element,
• wherein the at least one negative dR/dT resistive heating element and the multiple heater layers enable at least one of two-wire control and temperature control using heater resistance as a temperature feedback signal.

A heater system for heating a fluid comprising:

• a plurality of circuits arranged in a series within a flow path of the fluid,
• wherein at least one circuit of the plurality of circuits comprises a resistive heating element including a material having a non-monotonic resistivity vs. temperature profile with a local maximum, a local minimum and exhibiting a negative dR/dT characteristic over a predetermined operating temperature range along the non-monotonic resistivity vs. temperature profile;
• and
• wherein at least a second circuit of the plurality of circuits comprises a resistive heating element including a material having a positive dR/dT characteristic, and wherein the second circuit is adapted to allow for measurements of temperature across the circuit.