NPK Engineering & Service Co., Ltd.
Tested energy meters of this manufacturer are listed below
| WO No | 2077959 |
| QUA/CAL | |
| Report No | 05-1059 |
| Country | Thailand |
| Type | NP121D, NP123D, NP125D |
| Class (Wh) | 2 |
| Elements | 1-phase |
| Wiring | 2-wire |
| Connection | Direct connected |
| Technology | Mechanical (ferraris) |
| Frequency | 50 |
| Current | 5(25), 20(40) or 20(80) |
| Voltage | 220 or 230 |
| Register | Mechanical |
| Standards | IEC 62053-11 |