Project date 2003

The device is designed for registration of physical quantities and saving them in EEPROM memory. Due to small dimensions of the device and little energy consumption, it may be used not only as a laboratory tool for taking longlasting measurements, but also applied in cargo transportation control. Having installed the device among the products being transported, it will be possible to know whether the products have been kept in suitable conditions during their transportation or temporary storage. Such a control is important transporting the products which may lose their value due to inadequate temperature, lighting or humidity. Knowing the exact dates, when the products were kept under inadequate storage conditions, it can be easily ascertained who was responsible for the cargo at that particular time.

Business logic

In every each of its 5 channels, the device registers when the resistance is lesser than the selected threshold value. The time here is divided into portions of 1 minute. Also the air temperature and the luminous flux are registered. The periods of low resistance that have been recorded throughout the day are shared into 8 temperature and 8 light intensity intervals. Hence, the daily DR report consists of  8*8 = 64 spans characterized by temperature, light intensity and duration.

DR has an integrated clock according to which the daily reports are produced. The clock can be easily calibrated by connecting a specialized time unit to the DR. Here two successive green blinks indicate that the clock has been successfully calibrated. It should be noted that working without the previous steps is possible. However, the DR will not present any exact dates in its daily reports.

DR has 5 resistance-measuring channels along with one to measure each one of the following: temperature, light intensity and the power supply voltage. All the sensors connected to the device must be resistive with the resistance from 0.01 to 7 MOm.  The uncertainty of resistance cannot exceed to 10%. The temperature uncertainty depends on the type of thermal resistor that is being used and is approximately ±1..2. The luminous flux interval depends on the stability of photo-resistance and how it has been calibrated (temperature intervals are presented in degrees while light intensity intervals are displayed using quantized resistance of the photoresistor.

The data is stored to the replaceable EEPROM unit through consistent interface. Every minute if the channel’s resistance is smaller than the threshold, the device increases the X which is stored in memory according to its values of luminous flux and temperature. 1.5 bytes are devoted to every channel that registers duration leading to the total of 1.5*5 channels = 7.5 bytes per minute. Since a day contains 1440 minutes the comprehensive amount of bytes stored is 8*64 = 512 bytes per day. The red light blinks every 10 s. which indicates that the device is running (the actual light pattern is as follows: 8-18-28-38-48-58-0 (60) s., with the last flash indicating the measuring implementation at the end of the minute).

At the end of the day (00:00) the combined report of the previous day is stored to memory, the EEPROM is erased and set to hold the upcoming data. The memory unit (64 bytes) has the capacity to store 124 daily reports. After that the DR, quits its registering process and the indicating lights start blinking green.

The first time a memory unit is connected to the DR, the date is registered and after two successive red blinks further registrations begin.