Precise measuring of bulk materials in mines and hoppers helps to control raw material inventory at minerals and chemical industries
The primary application of FMCW 94/10 Millimeter Wave Distance Sensor is a high-accuracy non-contact level measurement of large volumes of bulk materials in hoppers and silos at minerals and chemical industries. The examples of use are hard-rock mines, cement hoppers, and other bunkers with adverse environmental conditions such as dust, corrosive gas, fog, high level noise. The Distance Sensor can also be used for liquid level measurement at huge industrial tanks where there is a fuzzy edge of liquid because of foam or vapor. The example of that application is volume measurement in tanks at large breweries.
Today most popular sensors types at industry applications that could meet the performance requirements for high-accuracy non-contact level measurement are laser, acoustic, microwave radar and millimeter wave radar. While laser and acoustic sensors work well in liquid level measurement, they become helpless at conditions of high dust level, strong air current and extremely high noise (underground blasting) that are common in hard-rock mines. Regarding microwave radar sensor, it emits too wide beam that limits its use at deep ore passes or at small-diameter bunkers. Because of wide beam, the microwave radar sensor cannot be used to explore surface profile. The precise detection of surface profile would be important for huge bunkers like cement hoppers to calculate actual volume of substance in the bunker.
Introducing passive mm-wave camera with additional incoherent illumination
While first commercial millimeter wavelength imaging security camera prototypes already come to the market, there are some obstacles on their way. Most important of them which come behind of the cost of the scanners, is relatively long exposure intervals required to get good image on the scanner screen. Why a long exposure required? It is easy to understand the answer if you can consider mm-wave scanner as a usual security camera, but only working in mm-wave band of spectrum. The long exposure is the effect of the fact that a human body emits very light mm-wave radiation while most of it comes at visible and infrared bands of spectrum. So to get a good picture in mm-wave band, you have to wait some time – exactly like first photographers had to wait for seconds to make pictures at the early days of photography.
By analogy with photography, to shorten an exposure in mm-wave band of spectrum, you can just light up an object that you shoot. This obvious solution has the only drawback, - it is not easy to design mm-wave sources of light (so called noise sources) that are true incoherent. Beams are incoherent if the phase relationship changes rapidly and randomly. Otherwise, when lighten up by coherent noise sources, an interference pattern consisting of dark and bright fringes may be formed resulting in practically unintelligible image on the screen of millimeter wavelength imaging security scanner.
This new 94GHz FMCW radar front-end is the production-run OEM subsystem product.
There are two versions of the radar front-end currently: 10mW and 200mW. The applications of Radar Front-end are object location in construction and in survey measurements, vehicle obstacle detection and collision warning in transport area, level sensing for loose/granular materials and other applications.
High power pulse noise source PNS series is used for illumination of target. Noise nature of probing signal avoids the problem of interference. Image obtained by means of noise radar allows to recognize target better then the image obtained by means of coherent radar.
The entire transmitter/receiver consists of the following elements:
ULM-11 unit is a microwave transmitter designed for continuos non-contact measurement of liquids, pastes and bulk solids. The unit operates in the 94 GHz frequency band that is unique for its market competitors. This frequency guaranties high-precision measurement that allows to use ULM-11 unit at a wide range of industrial and supply enterprises, including large-scale oil refineries, chemicals plants, commercial registration systems of petrol supply and so on. Because measuring through a window made of special material the ULM-11 unit measures level under extreme conditions, e.g. inside tanks with toxic and aggressive media.