| Sample No. | Open voltage(V) | Sample No. | Open voltage(V) |
| 1 | 230.5 | 6 | 228.8 |
| 2 | 230.1 | 7 | 229.4 |
| 3 | 229.6 | 8 | 230.2 |
| 4 | 230.4 | 9 | 230.4 |
| 5 | 229.8 | 10 | 230.6 |