Circuit arrangement to adjust and calibrate a MEMS-sensor device for flow measurement of gases or liquids

A method of adjusting and calibrating a heating element and an ambient temperature sensor, comprising:

• selectably coupling a first number of heating MOS transistors in parallel;
• selectably coupling a second number of ambient MOS transistors in parallel;
• removeably applying a bias current to a collective gate of the first number of heating MOS transistors, thereby creating a first current through a collective drain of the first number of heating MOS transistors;
• removeably applying the bias current to a collective gate of the second number of ambient MOS transistors, thereby creating a second current through a collective drain of the second number of ambient MOS transistors;
• determining a first voltage caused by the first current passing through the heating element;
• determining a second voltage caused by the second current passing through the ambient temperature sensor;
• and
• adjusting the first number of heating MOS transistors and/or the second number of ambient MOS transistors selectably coupled in parallel to substantially minimize a difference between the first voltage and the second voltage.

Circuitry for the adjustment and calibration of a heating element and an ambient temperature sensor, comprising:

• a) a heating connection configured to be coupled to the heating element;
• b) an ambient connection configured to be coupled to the ambient temperature sensor;
• c) a potentiometer having a first terminal, a second terminal, and a wiper, wherein the first terminal is coupled to the ambient connection;
• d) a reference connection configured to be coupled to the potentiometer wiper;
• e) an amplifier having a positive input, a negative input, and an output, wherein:
• 1) the negative input is coupled to the reference connection;
• and
• 2) the positive input is coupled to the heating connection;
• f) one or more heating metal oxide semiconductor (MOS) transistors selectably coupled in parallel and having a heating gate, a heating transistor source, and a heating transistor drain, wherein:
• 1) the heating transistor drain is coupled to the heating connection;
• and
• 2) the heating transistor source is configured to receive a supply voltage;
• g) one or more ambient MOS transistors selectably coupled in parallel and having an ambient gate, an ambient transistor source, and an ambient transistor drain, wherein:
• 1) the ambient transistor drain is coupled to the second terminal of the potentiometer;
• and
• 2) the ambient transistor source is configured to receive the supply voltage;
• h) a calibration MOS transistor having a calibration gate, a calibration transistor source, and a calibration transistor drain, wherein:
• 1) the calibration transistor source is configured to receive the supply voltage;
• 2) the calibration transistor drain is configured to receive a bias current;
• and
• 3) the calibration transistor gate is coupled to the calibration transistor drain;
• i) a selection switch having a first input, a second input, and an output, wherein:
• 1) the first switch input is coupled to the amplifier output;
• 2) the second switch input is coupled to the calibration transistor gate;
• and
• 3) the switch output is coupled to the ambient transistor gate and the heating gate.