| 摘要 |
PURPOSE: Provided is a thermal anemometer that separates sensor heating from sensor temperature measurement through a switched sampling technique to demonstrate several advantages over the more typical circuitry employing a bridge, which simultaneously heats the sensor and senses the ambient and velocity sensor temperature. CONSTITUTION: The thermal anemometer comprises an ambient sensor; a velocity sensor (R3); a sample and hold circuit; a switched heating voltage driver; a combined error amplifier (A1) and sample and hold circuit; a current source (201); a first switch (S1) electrically connected between the current source and the sample and hold circuit and between the current source and the ambient sensor; a second switch (S2) electrically connected between the current source and the switched heated voltage driver; and a third switch (S3) electrically connected between the combined error amplifier and sample and hold circuit and between the combined error amplifier and sample and hold circuit and the velocity sensor, wherein the combined error amplifier and sample and hold circuit are electrically connected between the sample and hold circuit and the switched voltage driver, wherein the sample and hold circuit comprises a switch (S3) and a capacitor (C1), wherein voltage is selectively applied across the velocity sensor, wherein the voltage is removed across the velocity sensor and the current source is selectively connected to the ambient sensor, wherein the ambient sensor comprises a resistance, the resistance creating a voltage across the resistance when current from the current source is applied to the resistance, the voltage being equal to a voltage across the velocity sensor, when the same amount of current is applied to the velocity sensor, and wherein the current source is selectively connected to the velocity sensor.
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