The DigiThermo is a device designed for measuring time and temperature used in chemistry laboratory. The circuit of Digithermo employs a 89C4051, 20-pin CMOS Microcontroller with built-in 4kB code memory. Temperature was measured by LM35D, National Semiconductor Temperature sensor producing 10mV/°C. The CA3162, 3-digit DVM converts dc output provided by LM35D and sends BCD output to port1 (P1.0-P1.3). The program resided in code memory of 89C4051 was written in ‘C’ language, thermo.c. The program read BCD output from the A/D converter, performs digital filtering,10-point moving average, and sends the output reading to a 16×1 line LCD display. A 10ms cputick was used as a timebase producing 1 s for time counting. The LCD displays time in 1 s and temperature in 0.1°C resolutions.
copyright from Wichit Sirichote