This is actually 8 bit A/D converter, connected via RS232 line to PC.
The main advantage is that it is connected by optocoupler/isolator.
All is driven by PIC16C84.
Schematic is included in dxf (AutoCad) and ps (PostScript) formats too.
Both programs, one for PIC and sonda.exe for PC are freeware and both are included in zip file. Program of PIC16C84 is easy reconfigurable for other processors from PIC16C family. This program is in fact never ending loop, which is 200 instructions long and PIC frequency is 8MHz. This causes that the loop is finished ten thousand times per one second. The main part makes two things. At first converts a voltage to number and then sends this number via RS232 to PC. Both activities are simultaneous and the number, related to voltage, is directly transmitted. Principle of conversion is based on well known approximation registry method. This is the reason why the Most Significant Bit (MSB) is sent as first. This device produces a data stream of ten thousand of samples per second.
This stream of samples is expected by the DOS program sonda.exe in PC. There is available a source code in zip file too. It is very very simple tool. But for me it was enough to view data on screen. All changes of program parameters are necessary to do directly in Turbo Pascal source code. The name of file input and output is "zzz.son".
Value of voltage is driven just only by a constant 5 in equation
str(5*(255-HL)/256:1:2,MVOLT[N]);MVOLT[N]:=MVOLT[N]+' V';in procedure SHOWVOLT(N:byte). The data input is controlled by procedure NEWDATA and SEM. I've stopped to work on this software just after a short time. What was done was enough for me...