The selection of on-site verification instruments may seem straightforward, but focusing solely on one or two parameters could result in insufficient functionality or failure to meet the accuracy requirements for formal inspections. It's essential to identify the key dimensions that truly impact practicality and evaluate them against your actual needs.

First: The accuracy grade must reach Level 0.05

This is the fundamental requirement for formal electrical energy metering verification work. Instruments with accuracy below 0.05 grade (e.g., 0.1 grade, 0.2 grade) lack sufficient uncertainty margin when verifying meters with 0.5 grade or higher accuracy, resulting in unreliable verification conclusions. They are unsuitable for official documentation or supplementary power consumption calculations. The HZ-3521A meets the 0.05 grade standard, complying with the basic requirements of the power industry for on-site inspection equipment.

Second: Does the clamp meter's current range cover the actual application

Standard configuration includes a range of 0.1 to 5A, suitable for the typical 1A and 5A rated currents of CT secondary circuits. If there are high-current conditions on-site (e.g., directly connected low-voltage high-current users), a clamp meter with ranges of 20A, 100A, or 500A should be selected. An inappropriate range selection may result in either undetectable signals or excessive errors within the range.

Third: Whether it supports both three-phase four-wire and three-phase three-wire connections

High-voltage users are mostly three-phase three-wire systems, while low-voltage users are mostly three-phase four-wire systems. Sometimes both types may be encountered during the same inspection. Ensure the instrument supports both wiring configurations to avoid incompatibility issues on-site.

Fourth: Is data management and export convenient

A large number of verification records need to be archived. Features such as USB export and direct Excel opening can significantly reduce the workload of re-entry. During selection, it is also essential to verify whether historical record queries and printing are supported; otherwise, on-site data can only be preserved through photos, making subsequent organization extremely inconvenient.