Fig. 9. Case 1: Water; testing results of the Neural Network using: (a) One NF, (b) Two NF, (c) Three NF, and (d) Four NF. Table 3 - Root mean square error and variance between neural network output and the ideal result when the content level varies from 0 to 100% Number of NF used 1 2 3 4 August 2021 Case 1 water RMS - Var 1.632 - 0.285 0.461 - 0.113 0.247 - 0.049 0.169 - 0.013 Case 2 salt water RMS - Var 1.820 - 0.240 0.884 - 0.331 0.293 - 0.043 0.173 - 0.020 Case 3 cooking oil RMS - Var 2.223 - 0.125 0.723 - 0.334 0.246 - 0.026 0.256 - 0.102 IEEE Instrumentation & Measurement Magazine Case 4 motor oil RMS - Var 3.347 - 0.198 0.471 - 0.153 0.274 - 0.089 0.159 - 0.022 25