| Charging voltage Vc (V) | |||
| Tube voltage (kV) | Measurement times | Average | SD |
| 50 | 5 | 3.07 | 0.007 |
| 60 | 5 | 2.92 | 0.006 |
| 70 | 5 | 2.84 | 0.005 |
| 80 | 5 | 2.75 | 0.012 |
| 90 | 5 | 2.63 | 0.004 |
| 100 | 5 | 2.53 | 0.003 |