This mini DigiThermo is a device specially designed for measuring and time and temperature in chemistry laboratory.

The following picture demonstrates the circuit diagram of DigiThermo.

1. The MCU: ATMEL 89C4051 CMOS Microcontroller with 4kB code memory, 128 bytes On-chip RAM and 8-bit Port1 and Port3.
2. The A/D chip: HARRIS CA3162, 3-digit DVM.
3. The A/D converter employs dual-slope integrator providing 10Hz sampling rate, while Digital output sent to MCU will be multiplexing four bit BCD started from MSD, LSD and NSD respectively.
4. Integrating capacitor: 330nF Polyester.
5. The 10k POT that connected to Pin 13 is a gain adjustment, while 50k POT to pin 8 and 9 is for zero adjustment purpose.
6. Pin 11 for HI and Pin 10 for LO for differential the input of converter.
7. LM35D used for temperature measurement tool.
8. The output signal is 10mV/°C.
9. First order low-pass filter acts as front-end hardware filtering is forming by a 100k and 0.02uF.
10. The 16×1 line LCD is connects in 4-bit interfacing to P1.4-P1.7.

The +5V power supply uses a 78L05 TO92 case with an external +9V adapter.