... variable frequency technology and micro computer control together, therefore, it can realize the full automatic voltage boost, stepdown, measurement and protection as ... frequency: 0.1Hz, 0.05Hz, 0.02Hz3. Measurement accuracy: 3%4. Positive and negative voltage peak errors: ≤ 3%5. Voltage ... would take a very high power, huge, heavy and expensive testers and this is not practical for field use. VLF ...