Air and gas flow velocity and temperature sensor probe
There is disclosed a handheld air flow velocity measurement probe that includes a bridge circuit assembly having an airflow velocity sensor that is a resistance temperature detector (RTD) and a digitally controlled resistive element to dynamically adjust and maintain the resistance of the velocity sensor within the overheat temperature predefined range. The velocity measurement also uses a separate temperature sensor to sense the temperature of the air or gas flow. A humidity sensor is also included remote from the other sensors to measure humidity in the gas flow to be measured. All of the above described components are housed at a probe tip instead of a base as in most standard handheld probes and the digital interface at the probe tip allows the user to replace a bulky, expensive telescoping antenna with stackable extender scheme.
1. An air velocity sensor apparatus adapted to measure air and gas flow velocity and temperature comprising:
a bridge circuit assembly including a bridge circuit coupled to an operational amplifier and a power output amplifier, the bridge circuit including a first leg with a heated velocity sensor and a first reference resistor, the velocity sensor configured to operate within a predefined overheat temperature range which is above an ambient temperature, the bridge circuit having a second leg comprised of reference resistors and a digitally controlled resistive element to dynamically adjust and maintain the resistance of the velocity sensor within the overheat temperature predefined range, the operational amplifier applying a DC voltage to enable the velocity sensor to be heated to a target temperature within the overheat temperature range;
a gas flow temperature sensor for measuring the temperature of the gas or air flow to be measured; and
an analog to digital converter coupled to an output of the temperature sensor and to an output of the bridge circuit assembly
wherein the bridge circuit assembly, the gas flow temperature sensor and analog to digital converter are located in a probe tip housing, the probe tip housing having a window or opening that is adapted to expose the velocity sensor and the temperature sensor to an air and gas flow.
2. The air velocity sensor apparatus of claim 1 , wherein the power output amplifier of the bridge circuit assembly operates in a range less than about 900 microwatts, thereby enhancing the determination of temperature within the sensor apparatus as the velocity sensor is exposed to an airflow to be measured.
3. The air velocity sensor apparatus of claim 1 , further comprising a humidity sensor located away from the velocity sensor and exposed to the same air flow as the velocity and temperature sensors, thereby increasing the accuracy of air velocity measurements by factoring in humidity levels in air flow.
4. The air velocity sensor apparatus of claim 1 , wherein a second temperature sensor and humidity sensor are provided in a single device to enhance the ability to make a humidity measurement which is very sensitive to temperature.
5. The air velocity sensor apparatus of claim 1 , further comprising a flexible printed circuit board having the velocity sensor coupled at a distal end and the temperature sensor located thereon and away from the velocity sensor and having a proximal end of the flexible printed circuit board coupled to a connector in the probe tip housing, the flexible printed circuit board extending past the probe tip opening to expose the velocity sensor through the probe tip opening.
6. The air velocity sensor apparatus of claim 1 , wherein the probe tip housing is adapted to couple to a probe handle including therein a controller, a memory unit and a display electrically coupled to the bridge circuit assembly for processing and storing data generated by the bridge circuit assembly and temperature sensor.
7. The air velocity sensor apparatus of claim 6 , wherein the probe handle further comprises an RF communications module for wireless communication with a base unit.
8. A data collection system including the velocity sensor, probe tip and probe handle of claim 7 , further comprising a mobile or wireless software applet operating on a mobile communications device configured to communicate with the controller unit and memory in the probe handle.
9. An array of air velocity sensor apparatus of claim 1 configured for measurement of air flow patterns in an air duct, the array comprised of a plurality of air velocity apparatus connected in series with at least one coupling member interposed between each air velocity apparatus such that each probe opening is disposed in different parts of an air duct.
10. The air velocity sensor apparatus of claim 1 additionally comprising a non-volatile memory unit containing calibration data located in the probe tip housing.
11. The air velocity sensor apparatus of claim 1 wherein the probe tip housing is comprised in a removable probe tip.
12. The air velocity sensor assembly of claim 6 wherein the probe tip housing is comprised in a removable probe tip.
13. An air velocity sensor assembly adapted to measure air and gas flow velocity and temperature comprising:
a probe tip housing having an opening therein;
a bridge circuit assembly disposed within the probe tip housing and including a bridge circuit coupled to an operational amplifier and a power output amplifier, the bridge circuit including a first leg with a heated velocity sensor and a first reference resistor, the velocity sensor configured to operate within a predefined overheat temperature range which is above an ambient temperature, the bridge circuit having a second leg comprised of reference resistors and a digitally controlled resistive element disposed within the probe tip housing and adapted to dynamically adjust and maintain the resistance of the velocity sensor within the overheat temperature predefined range, the operational amplifier applying a DC voltage to enable the velocity sensor to be heated to a target temperature within the overheat temperature range;
a gas flow temperature sensor disposed within the probe tip housing for measuring the temperature of the gas or air flow to be measured;
an analog to digital converter disposed within the probe tip housing and coupled to an output of the temperature sensor and to an output of the bridge circuit assembly; and
an extension member having a proximal and a distal end, the extension member having an electrical coupling member disposed therein for coupling the probe tip housing located at the extension member proximal end to an electrical connector at the distal end of the extension member.
14. The air velocity sensor assembly of claim 13 , further comprising a humidity sensor disposed within the probe tip housing and on a printed circuit board connecting the bridge circuit assembly and the temperature sensor outputs to the analog to digital converter.
15. The air velocity sensor assembly of claim 13 , wherein the extension member is selected from a group consisting of an articulating probe member having an angular range of between zero and at least 90, a cable member, and a goose neck type member.
16. The air velocity sensor assembly of claim 13 , further comprising a plurality of extension members coupleable in series and configurable to have various lengths to enable air velocity measurements remote from a user of the velocity sensor assembly.
17. An array of air velocity sensor apparatus of claim 13 , configured for measurement of air flow patterns in an air duct, the array comprised of a plurality of air velocity apparatus connected in series with at least one coupling member interposed between each air velocity apparatus such that each probe opening is disposed in different parts of an air duct.
18. The air velocity sensor assembly of claim 13 , wherein the probe tip housing is adapted to couple to a probe handle including therein a controller, a memory unit and a display electrically coupled to the bridge circuit assembly for processing and storing data generated by the bridge circuit assembly.
19. The air velocity sensor assembly of claim 13 additionally comprising a non-volatile memory unit containing calibration data located in the probe tip housing.
20. The air velocity sensor assembly of claim 13 wherein the probe tip housing is comprised in a removable probe tip.