DATA ACQUISITION
Thanks to the kind assistance of company MAXIM which we thank here, and which sent to us
a few samples, we started to carry out what we considered for a long time: digitalization
of the received signals.
We built a small a/d converter with one channel with a max 187 according to the
model described on the site of Radio-sky publishing. This system uses the port printer of a PC .
We use an old HP VECTRA with 33mhz clock that is not expensive and does not put interference
to the receivers .
Here is the schematic :
It works under DOS .Any old pc can do it .
We wrote the programs in qbasic to make measurements: one which acquires, records measurements
and records them on the disc, and another program which reads a file already recorded.
The recorded files include the number of the measurement, the measured value
and the hour according to the hour of the PC. This file is in ASCII, its name is formed
from the date, and it can be read by any standard editor . It can be used with
free software like GNUPLOT, after one very simple modification by a standart editor
to replace the commas which separate the data (it is standart in any sequentially recorded file)
by a space necessary for the reading by Gnuplot. The speed of acquisition is variable
even during the acquisition, the reading rate also, and the two speeds are independent.
One can be used to acquire very quickly, until 100 measures/second on a fast PC, and read
again slowly.
Let us specify that the sub-routine of the program of acquisition is a modified version
of a routine published on the site of Radiosky publishing.
The two programs are:
to do data acquisition
to read previously acquired data