The 3NJ6940-3BH12 combines a 1 A secondary with Class 0.5 accuracy for SENTRON 3NJ6 in-line fuse-switch-disconnectors. It sits between the entry-level Class 1 variants and the legal-for-trade calibrated 3BH13 — delivering high precision for sub-metering and remote monitoring without the billing premium.

Why combine 1 A secondary with Class 0.5 accuracy?

This pairing is aimed at installations where the CT and the meter are far apart. A 1 A secondary keeps I²R losses in the connecting cable under control over distances of 15 metres or more. Class 0.5 halves the error margin compared to Class 1 (±0.5% vs ±1% at rated current), which matters when aggregate energy data feeds into cost allocation, efficiency tracking, or tenant sub-metering. You get precision-measurement data at the remote meter without the calibration cost and lead time of the 3BH13.

How does this differ from the calibrated 3BH13?

Both share the same 300/1 A ratio and Class 0.5 accuracy. The difference is purely the legal-for-trade conformity assessment. The 3BH12 measures with identical precision — it simply lacks the factory calibration certificate required for revenue billing. For internal cost allocation, energy management systems, and precision monitoring, the 3BH12 delivers the same performance at a significantly lower price and with standard 3-day availability.

Frequently Asked Questions

What cable distance can I bridge with 1 A secondary?

With 2.5 mm² copper control cable, a 1 A CT can drive 50 metres or more before burden limits become a concern. With 5 A secondary, the same cable would reach its VA limit at roughly 10 metres. Always calculate total burden: meter VA + cable I²R must stay within the CT's 5 VA rating.

Can this CT be used with a 5 A input meter?

Directly, no. A 1 A CT requires a meter with 1 A nominal current input — or an interposing 1A/5A converter. Most modern digital meters accept both 1 A and 5 A inputs via configuration. Check your meter's specification before ordering.