Home › Knowledge Center › How Much Overvoltage and Overcurrent Can the Unit Endure?
How Much Overvoltage and Overcurrent Can the Unit Endure?
Meters are rated for a normal measuring range, but they can also survive limited overloads. The datasheet usually states these as continuous overload and short-time overload figures. Staying inside them protects the instrument and its accuracy.
Typical ratings (sample values, confirm on the datasheet)
| Continuous voltage | 120% of rated range |
|---|---|
| Short-time voltage | 2 × rated range for 1 second |
| Continuous current | 120% of rated range |
| Short-time current | 10 × rated current for 1 second (via CT or shunt as specified) |
| Isolation | 2 kV, 1 minute, between input and supply |
These numbers are placeholders for the sample site. Replace them with the tested values for each model.
What the terms mean
- Continuous overload: the level the meter can sit at indefinitely without damage, though readings may go out of range.
- Short-time overload: a higher level tolerated only for a stated time, such as 1 second, then it must return to normal.
- Inrush: a brief surge at switch-on, common with motors, transformers and LED drivers. Choose a meter whose short-time rating covers it.
Practical advice
- Pick a range so normal readings fall between 20% and 90% of full scale.
- For transformers and motors, size for inrush, which can be several times the running current.
- Use a CT or an external fuse where overloads are likely.
- Overloading beyond the short-time rating can damage the unit. Check the warranty terms.