Laboratory and on-line microwave moisture meters

On-line microwave MICRORADAR113C2 moisture meter

The MICRORADAR113C2 moisture meter is designed for the continuous moisture measurement of granular and powdered materials. The devises sensor can be mounted in places of material free fall in pipes. The MICRORADAR113C2 is suitable for the measurement of a variety of materials, including kaolin, alumina, aluminum oxide, coal, salts, minerals, sand, and other materials with intermediate to low moisture content (0,5 to 30%), and is easily incorporated into automatic process control systems. The device is appropriate for working under the condition of high temperatures and dust content, high abrasiveness and aggressiveness of material.

In order to create a continuous flow of the material, we employ a screwfeeder (see figure) to fill and empty the measuring space with the material.The feeding mechanism is mounted on a bunker wall or a pipe with a mounting flange, so that the material would fall into a feed box. At the top of the feed box there is a shutter that controls the amount of material fed into the measuring space. Unloading the sensor is carried out continuously with a screw feeder. A screw feeder is driven by geared DC electromotor (5 ...12V). The voltage of the motor is generated in the Unloading Control Unit, which issupplied together with sensor block and is mounted next to sensors.

How The Meter Works

The meter is installed with the transmitter and the receiver placed across the material under test. An electromagnetic wave is generated by the transmitter and passed through the material, and the receiver detects the amount of electromagnetic energy absorbed by the water in the material. Despite the complexity of the physical structure of the material, there is usually a simple linear relationship between the moisture content and the amount of energy absorbed (at least in a limited range of moisture content). This relationship may be written in the form: N=8.7 AWrd Where: N microwave attenuation by material, Awater absorption, W moisture content of material,d thickness of material, r density of material. The moisture meter ensures self-acting correction of measuring results at a material temperature variation, has a current output and a serial port RS- 485 for data transmission to a computer. The value of moisture is displayed on a display diagram board of a microprocessor unit and is conversed to analogue outputs 4-20 mA and 0-5 V.Through the channel RS485 moisture, temperature and the sensors' signals can be transmitted to the computer. The complete set of delivery of the device includes the program of storage and displaying of moisture real-time, that allows to enter into the computer, to watch, to store and to print the information on moisture for any span. A moisture measurement accuracy is from 0,15 % up to 1 % depending on a moisture range considering inaccuracies of the sample choice and moisture measuring by a standard method, for example, by oven.

The basic technical characteristics:

Range of moisture measurement . . . . . 0,5-3%	Basic measurement inaccuracy. . 0,15 %abs.;
Range of moisture measurement . . . . . 3-15%	Basic measurement inaccuracy. . 0,5 % abs.;
Range of moisture measurement. . . . . 15-30%	Basic measurement inaccuracy. . 1,0 % abs.;
Unitized analogue output (alternative)	(4 … 20; 0-5; 0-20) mA
Serial port for data transmission to PC	RS-485
Power supply	=24 V or 110 or 220 V / 50 Hz
Power consumption	No more than 50 VA
Fulfilment of housings of units	IP54