Main technical features of the device
The DNSZ MP-03 device is composed of a central unit and of the attached distant transmitters.
The central unit is installed in an industrial metal sheet box of the size of 400x400x210 mm. The front carries the main switch, the operating switches to be used to starting and stopping the process as well as the flag and the keyboard of the computer. The central unit card, the digital inlet and outlet card and the supply unit of the entire device are installed in the box. The central unit card contains the EEPROM storage unit to store the measured data (96 kbyte non-volatile memory), the RS232 line leading to the LCD flag and keyboard and the RS485 line connecting the distant transmitters. The LCD can display 4x20 characters and its background is lit. The RS485 line has galvanic insulation and is protected against over-voltage, an absolute necessity because of the large geometric size of the drying tower.
Through the RS485 line intelligent remote transmitters (having their own processors) are linked to the controlling device. The controlling device receives 2 temperature distance transmitters for measuring the temperature of the drying air and the internal temperature of the grain, 1 instrument measuring relative humidity content and three instruments taking the moisture content of the grain.
The temperature distance transmitter contains two sensor elements operating with exactitude of 0,5 °C 0.5 °C; the instruments calculate the average of the data before transmitting it to the central unit.
The instrument measuring relative humidity content takes the relative humidity of external air in the range of 20-90%. As supplementary service the instrument also takes the temperature of external air and transmits it to the central unit.
The instruments taking the moisture of grain measure moisture on the capacitive principle. Their own internal processors contain automatic temperature compensation and corrective table depending on the type of grain. They are made of two types: one version is connected to the large-capacity electrode system of the drying tower, while the other version measures the small-capacity electrodes of the incoming grain. Eight pieces of internal correction tables can be placed in the memory, enabling to measure eight types of grain.
The distant transmitters discussed above transform into (12-byte) series signal the physical characteristics to be measured by analogue-digital conversion after the relevant analogue signals are obtained. The series line is an RS-485 line with galvanic insulation and with protection against over-voltage and it its through its cable that the supply voltage reaches the distance transmitters. The control box has 8 digital input- and 8 digital output channels to control the technological signs. The input channels are of 24V DC level and the output ones are 250mA type relays.
The device regulates the time during which the grain passes through the drying tower, thus setting the moisture content of the discharged grain to the required value. Regulation is performed by setting the speed of the discharging conveyor belt (in case of variability ) or by cyclic switch-on and switch out of the conveyor belt. Leading back the sign from the own discharging relay of the drying tower it is possible to make evaluation and obtain information on the operation of the dryer even in case of non-automatic operation.
During the drying period the values taken are stored once every ten minutes in the non-volatile memory of the computers. These values can be checked for the interval of the last 30 days or can be transferred through a data saving device –an optional accessory- to a remote PC, where they can be evaluated with the help of, say, a Microsoft Excel program. The following data are stored:
- moisture of the downloaded grain
- moisture content of the grain on the bottom of the warm zone
- moisture of departing grain
- relative humidity of air
- temperature of drying air
- grain temperature in the middle of the warm zone
- grain temperature on the level of instruments measuring moisture content
- calculated discharging time and interval
- measured discharging time and interval
- type of grain
- identification of operator
An precise time stamp (provided by a real-time clock in the device) is attached to all measured values. The management of the time format is Y2K proof and the device can handle leap years and relevant date problems up to year 2099.