AUTOMATIC SYSTEM FOR TESTING OF DYNAMIC QUALITY OF PC PLUG-IN A/D BOARDS

Pokorny M, Roztocil J, Haasz V.

CZECH TECHNICAL UNIVERSITY, FACULTY OF ELECTRICAL ENGINEERING,
DEPT. OF MEASUREMENT
TECHNICKÁ 2, CZ-16627 PRAGUE 6, CZECH REPUBLIC


The important parameter of the dynamic quality of PC plug-in AD boards is a number of effective bits. The method of a sine wave curve fitting was used for determination of this parameter in the described system. The number of effective bits is determined in this case from a difference between the measured samples of an input spectral pure sine wave and a fitted sine wave using the algorithms published in [1]. The measurement of parameters of one plug-in board in the wide frequency range of an input signal is unfortunately time-consuming. Besides it is necessary to measure several pieces of each type of tested AD board to get objective common results of this type. It was a reason, why an automatic system for these tests was realized.

The automatic test system consist of a sine wave generator controlled by IEEE 488 bus, a PC with a tested plug-in board and a software package, which ensures a control of the generator and of the tested plug-in board, and a processing of measured data. The high quality generator have to be used for this method (spectral purity -80dB for 12 bit AD boards). The generator which is build in the Lock-in amplifier SR 830 DSP, satisfies this parameters and was used for this purpose in the designed system.

The software package was created in LabWindows/CVI environment as an application under MS Windows. It consists of two parts, the first for a data acquisition and the second for a data processing and a results presentation. This solution makes it possible to use the part of the data processing and the results presentation also for a previously measured data, which were stored in a file.

The results are presented in a table or in a graphical form. They can be also stored in a file for a future statistical processing or publishing. The program is easy controlled using a button menu.