**2. Data acquisition**

The National Instrument Data Acquisition Toolbox™ provides functions for connecting MATLAB® to data acquisition hardware. The toolbox supports a variety of DAQ hardware.

With it, one could configure data acquisition hardware to read data into MATLAB or SIMULINK for immediate analysis. One can also send out data over analogue or digital output channels provided by data acquisition hardware. Depending on which card is used, one can configure several channels, as input or output, digital or analogue. The card is interfaced to the process through a screw type connectors SCB-68 Quick Reference Label. Figure(4) shows the real connector board.

**Figure 4.** Interfacing connecting card to PCI 6221

Data Acquisition Toolbox lets you make a variety of measurements directly to MATLAB or SIMULINK, without the need to convert the data, so one can directly read the pH from the probe through the signal conditioning circuitry. In our case, only analogue input channel0 and output channel0 are used.
