FIELD

Aspects of the disclosure relate to apparatuses and methods for measuring humidity in air. In particular, certain aspects are directed to humidity meters and associated methods of using humidity meters to measure relative and/or absolute humidity from an airborne vehicle.

BACKGROUND

The measurement of fine scale vertical and horizontal gradients of atmospheric water vapor concentration, or humidity, is of critical importance in the fields of environmental studies and atmospheric electromagnetic propagation research. Fine scale gradients of humidity can impact electromagnetic propagation (EMP) in the ultraviolet (UV), visible (VIS), and infrared (IR), as well as in the radar and communication wavelength bands. To resolve these gradients with adequate spatial resolution on a fast moving aircraft, a humidity meter with a fast time response is required.

On larger airplanes or other airborne vehicles, sophisticated optical instruments, such as krypton hydrometers, can be used to achieve the necessary fast response measurements (i.e., measurements made within an acceptable predetermined amount of time). However, these sophisticated optical instruments are often large and heavy, and are not practical or even feasible for use on small or medium sized airborne vehicles, such as unmanned aerial vehicles. Accordingly, it would be advantageous to have a humidity meter for small to medium sized unmanned aerial vehicles with adequate sensitivity, accuracy and response time to measure the fine scale atmospheric gradients of absolute humidity critical to assessing refractivity anomalies that impact EMP in, for example, the radar and communication wavelength bands.

One or more aspects described herein overcomes these limitations and allows the measurement of relative and absolute humidity with high accuracy, sensitivity and fast response time.

SUMMARY

The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. The summary is not an extensive overview of the disclosure. It is neither intended to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure. The following summary merely presents some concepts of the disclosure in a simplified form as a prelude to the description below.

Aspects of the disclosure provide a small size, lightweight humidity meter with a sensor that permits measurement of relative and/or absolute humidity in air with high accuracy, sensitivity, and fast response time. Such a device can be used to measure relative and absolute humidity onboard airborne vehicles for the characterization of fine scale vertical and horizontal gradients of atmospheric water vapor concentration. Other applications include industrial and residential air quality and airflow monitoring.

In accordance with a first aspect, a humidity meter includes a humidity sensor and a heating device oriented towards the humidity sensor. A signal generator is configured to modulate a power output of the heating device, and a lock-in amplifier is configured to demodulate a response signal of the humidity sensor as induced by the modulated heating device.

In accordance with another aspect, a humidity meter may include one or several capacitive humidity sensors, a heating device, a temperature sensor, a pressure sensor, a function generator, a lock-in amplifier and a microcontroller.

In accordance with yet another aspect, the response signal of a capacitive humidity sensor as induced by the modulated heating device may be a change in the capacitance of the humidity sensor; and a lock-in amplifier may be configured to demodulate and measure the said response signal.

In accordance with a further aspect, a method of measuring humidity includes the steps of providing a humidity sensor positioned along a channel, a heating device positioned opposite the humidity sensor along the channel, and a controller including a signal generator and a lock-in amplifier; providing an airflow along the channel; modulating a power supply to the heating device using the signal generator; and demodulating a response signal of the humidity sensor induced by the modulated heating device.

Some advantages of one or more aspects described herein include fast response time, high accuracy and sensitivity, light weight, low cost, low power consumption, and a lack of moving parts. This permits the usage of humidity meters on small and medium sized unmanned aerial vehicles (UAV) to improve electromagnetic maneuver warfare (EMW) and intelligence, surveillance and reconnaissance (ISR) sensor performance prediction, as well as weather hazard sensing, avoidance and mitigation, and forecasting

These and additional features and advantages will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure and detailed description of certain exemplary embodiments.

