The test current is limited by a simple current limiting circuit and is measured by monitoring the voltage across a resistor. The test current is maintained at a nominal 2 A, and as the measurement is ratiometric, the reading is unaffected by any current variations.
- High test current
- Four terminal measurement
- Two measuring ranges (2000 m? an 20,00 m?) and maximum resolution of 0,01 m?
- Protected against inadvertent connection to the mains supply
The instrument has a 31/2 digit LED display to facilitate use in low light levels. Two LED's on the front panel indicate battery condition and whether test current is flowing when a measurement is being made. A neon lamp indicates the presence of a dangerous voltage if the test spikes are accidentally placed across a live circuit. This warning takes place whether or not the instrument has been switched on.
The ohmmeter is protected up to 240 V a.c. by a relay circuit that keeps the instrument in a safe mode isolated from the mains supply. Again, this safeguard is effective whether or not the instrument has been switched on.