Design of the excitation source of a conductivity measuring device based on AD9833

An excitation source for a conductivity measuring device has been designed based on AD9833 by analyzing the basic features of the excitation source.The hardware of the excitation source include the AD9833 waveform generator,polarity setting module,a third-order Sallen-Key filter module,and the human-machine interface.The software design of the system is based on an IAR embedded workbench by using modular programming methods with the C language.Three aqueous samples were tested using this excitation source,and the test results were compared with the results obtained using a DDSJ308A conductivity measuring device.The experimental results indicated that a larger measurement error would be introduced when the excitation signal is lower(1 kHz),while the accuracy of the measurements would be enhanced when a higher signal(2 kHz) is used.