For evaluating the proposed method, for cases were considered and results were given in table 3, table 4, table 5 and table 6. The sensor and actuator was connected as shown in figure 1 and output voltage values were noted using multi-meter (DMM) or voltmeter before connecting to DAQ. Before started working on propose, the user needs to find the full operating range of the process.
In this study, Level sensor and control valve were considered, the full operating range was measured by supplying a water into the process tank of 1.28 V for 0 cm and 5.14 V for 90 cm liquid level. These values were obtained by varying the DRB (R1) to appropriate value, the value in the DRB is adjusted as per the requirement of the user, the objective is to convert the (4-20)mA current signal to (1-10)V. Simply by adjusting the DRB the user can get some random values. But the user must ensure the value should in the range of (1-10) V.
In similar way, for (0 to 100) % control valve i.e., (open to close) signal range was measured by adjusting the DRB resistance values to appropriate values and the respective voltage values were given in table 2. Four cases were considered for analysis based on output signal range, (1-9) V for case 1, (1-8) V for case 2, (1-7) V for case 3 and (1-6) V for case 4.
After obtaining the input and output signal range values, the user were framed four step formula in the LabVIEW and respective values were given in table 3, table 4, table 5 and table 6.
From the above cases 1 to 4, it can be seen that the sensor range (4-20) mA was initially converted to (1.28-5.41) V and by considering the output signal range as desired range values, the formula was framed for four different output ranges. It clearly shows that the mapping of input and output signal was done and gives a greater result in real time application. Once the formula given in table 2 was implemented, the controller design will be easy for the user to get proper closed loop results.