# Development of Heavy Metal Potentiostat for
## 3 Results and Discussion  
### Accuracy and Noise Measurement  
Based on Equations (5) and (6), the percentage error (PE) of the PCP and CMP of the HMstat, and the CMP of Rstat was shown in Figure 5. The PE obtained by the HMstat for both PCP and CMP was less than 5% for every types of \(V_{ap}\). Generally, the lowest error was observed when the \(V_{ap}\) was at the constant potential. The highest error was obtained for the ramp potential followed by SWV potential. The constant potential produced significantly lower error compared to the ramp and SWV. This was due to the fluctuated signal of the ramp and SWV, which may have led to higher noise generation. Moreover, these patterns were also observed in the PE of the CMP for Rstat. However, the PE obtained for the CMP of the Rstat was higher compared to HMstat for all types of \(V_{ap}\).  
Table 3 shows the performance HMstat and Rstat, including the lists of PE, accuracy, and noise measurement. The accuracy was measured based on Equations (3) and (4) and the noise measurement was determined based on the standard deviation of the data. The measurement of the accuracy was related to PE, and the accuracy of HMstat was higher than 95% which is within the precision rate of the components used. Moreover, HMstat showed better accuracy compared to Rstat in a similar pattern as in PE. The degradation of accuracy might have been caused by a higher noise current, as \(V_{ap}\) changed from constant potential to ramp potential, and to SWV. The lowest noise current was obtained for constant \(V_{ap}\) (5 nA for both \(V_{ap}\) of \(-\)0.5 V and +0.5 V). The noise current increased to 6 nA when ramp \(V_{ap}\) was applied. The highest noise current of 7 nA has been obtained for SWV \(V_{ap}\). This was due to the fluctuated signal of ramp, and SWV, which may have led to higher noise generation.  
Figure 5: Accuracy of the current measurement part (CMP) for HMstat and Rstat.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Type of \(V_{ap}\)**} & \multirow{2}{*}{\(V_{ap}\) **(V)**} & \multirow{2}{*}{**Potentiostat**} & \multicolumn{2}{c}{**PE (\%)**} & \multicolumn{2}{c}{**Accuracy (\%)**} & \multicolumn{2}{c}{**SD (\(\mu\)A)**} \\ \cline{4-9}  & & & **PCP** & **CMP** & **PCP** & **CMP** & **SD** \\ \hline \multirow{4}{*}{Constant} & \(-\)0.5 & HMstat & 2.575 & 1.445 & 97.425 & 98.555 & 5.215 \\  & & Rstat & \(\times\) & 1.961 & \(\times\) & 98.039 & 6.934 \(\mu\) \\ \cline{2-9}  & \(+\)0.5 & HMstat & 3.373 & 1.567 & 96.627 & 98.433 & 5.337 \\  & & Rstat & \(\times\) & 4.063 & \(\times\) & 95.937 & 14.364 \(\mu\) \\ \hline \multirow{2}{*}{Ramp} & \(-\)1 to \(+\)1 & HMstat & 2.470 & 4.121 & 97.530 & 95.879 & 6.789 \\  & & Rstat & \(\times\) & 8.998 & \(\times\) & 91.002 & 20.664 \(\mu\) \\ \hline \multirow{2}{*}{SWV} & \(-\)1 to \(+\)1 & HMstat & 4.899 & 4.219 & 95.101 & 95.781 & 7.287 \\  & & Rstat & \(\times\) & \(\times\) & \(\times\) & \(\times\) & \(\times\) \\ \hline \end{tabular} \(\times\) not tested due to the data not being able to be obtained.  
\end{table}
Table 3: Performance of HMstat and Rodeostat (Rstat) in term of percentage error (PE), accuracy, and noise current measurement (SD).