Automated INL and DNL Testing System as a Didactic Laboratory Application

Measurement systems are based on analog to digital converters because they offer easy data processing, storage and transmission. Since the majority of the measuring instruments includes ADCs, it is important for students studying Electric and electronic measurements to learn about the parameters of an ADC. INL (Integral nonlinearity) and DNL (Differential nonlinearity) are two of the most important parameters that characterize an ADC, but the process is also time consuming. The present paper presents an automated test system for didactic laboratory. The DUT is a NI DAQ card, the reference instrument is a high accuracy voltage source and the associated software is developed in LabVIEW. The tested parameters are calculated automatically during the process and are displayed on graphs as well as stored in a data file. As conclusions the results are analyzed for comparing the digital code data and the calibrated voltage data.