Electronic Measuring Energy Meters

Q: How do I know what size current transformer I need for my meter?

Choose a CT rated at around 125% of your expected peak load. For example, a circuit with a 160A maximum demand would typically use a 200A CT. Check the meter accepts the secondary output of the CT — most Owen Brothers meters use standard 5A, 1A, or millivolt output depending on the model. Call our team on +44 (0) 161 624 6211 for help selecting the right CT. Browse current transformers: https://owen-brothers.com/test-terminal-blocks/current-transformers.html — CT132 Solid Core Current Transformer: https://owen-brothers.com/ct-132-solid-core-current-transformer.html

Single Phase

OB112 45A, MID Approved, DIN Rail, Direct Connected Digital Meter

£17.76

OB115-MOD 60A, 15m CT Lead, MID Approved, DIN Rail, CT Operated, RS485, Bi-Directional Digital Meter

£43.00

OB115-MOD 100A MID Single Phase CT Online Monitoring Kit with 12 Months Remote Monitoring Access

£254.21

Three Phase

OB4371CT MID Approved, DIN Rail, CT Operated, RS485, Bi-Directional Digital Meter

£84.00

OB4374 Three Phase Multi Circuit Digital Meter - Millivolt CT - In IP66 Enclosure

£205.00

OB4371 CT Three Phase Multi-Function MID Meter in IP66 Enclosure

£178.00

Best Sellers

Metro 80A Single Phase Pre-Payment Meter - MET001

Regular Price £39.60 Special Price £36.00

IC Smart Card

£1.55

OB112 45A, MID Approved, DIN Rail, Direct Connected Digital Meter

£17.76

Portable Kits

Frequently Asked Questions

Do I need a MID approved meter to charge tenants for electricity?

Yes. If you are billing tenants based on meter readings, the meter must hold MID approval under the GB Measuring Instruments Regulations. MID certification confirms the meter has been independently tested to a defined accuracy standard. Using a non-MID meter for billing puts you in a difficult legal position if a tenant disputes a charge.

All Owen Brothers sub-meters sold for billing applications are MID approved. You can confirm MID status on any product page before you buy.

What is the difference between a single phase and three phase energy meter?

A single phase meter measures electricity on a two-wire supply (live and neutral), typically used for smaller properties, offices, and light commercial units up to around 100A. A three phase meter measures across three live conductors and is used for larger commercial premises, industrial equipment, and any supply where demand regularly exceeds what a single phase can handle.

If you are not sure which supply you have, check your distribution board. A three phase supply will have three separate circuit breakers for the incoming supply.

Can I install a sub-meter myself or do I need an electrician?

For direct connected meters on supplies up to 100A, a competent DIYer can often fit a DIN rail meter with the supply isolated. However, for CT operated meters, three phase supplies, or any work on the main incoming supply, a qualified electrician is strongly recommended.

All electrical work in the UK must comply with BS 7671 wiring regulations, and any work on the main consumer unit or incoming supply should be carried out by a Part P registered electrician.

What does CT operated mean on an energy meter?

CT stands for current transformer. A CT operated meter uses external current transformer clamps fitted around the supply cables rather than having the full load current pass through the meter itself. This is needed for loads above around 65A on a three phase supply or 100A on a single phase supply.

The CTs produce a small secondary current proportional to the actual load, which the meter reads and converts to a kilowatt-hour figure. CT operated meters are standard for most commercial sub-metering installations.

How do pre-payment electricity meters work for landlords?

A pre-payment meter requires the tenant to load credit before using electricity. The tenant tops up using a smart card or key, and the meter deducts credit as electricity is used. When credit runs low, the meter gives a warning and disconnects the supply when it reaches zero.

For landlords, this removes the risk of unpaid utility bills and avoids disputes over usage. Owen Brothers supply the Metro range of pre-payment meters, which use IC smart cards and are widely used in HMOs and multi-tenancy properties across the UK.

What is a Rogowski coil meter and when would I use one?

A Rogowski coil is a flexible, air-core sensor that wraps around a conductor to measure current. Unlike a standard current transformer, it has no rigid iron core, so it can be bent and threaded around large busbars, awkwardly positioned cables, or existing live conductors without disconnecting the supply.

Rogowski coil meters are used for industrial three phase applications with high currents, for retrofit installations where the supply cannot be isolated, and anywhere the physical size or position of the conductors makes a standard CT impractical.

Do your meters come with free delivery?

Yes, Owen Brothers offer free delivery on all orders over £99. Orders below that threshold are charged at standard rates. Most items are held in stock at the Oldham warehouse and despatched the same day or next working day.

International shipping is also available to over 50 countries if you need meters delivered outside the UK.

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What is remote monitoring for energy meters and how does it work?

Remote monitoring lets you read meter data without visiting the site. Owen Brothers use LoRa (Long Range) wireless technology. A small OBM-LoRa unit attaches to the meter and transmits readings wirelessly to a gateway, which feeds into the ReadMyMeter online portal.

You can view consumption in real time, track usage across multiple sites, and produce reports for billing, all from a laptop or phone. It is particularly useful for landlords and facilities managers with meters spread across several properties.

How do I know what size current transformer I need for my meter?

The CT ratio must match or exceed the maximum continuous current of the circuit you are metering. As a general rule, choose a CT rated at around 125% of your expected peak load to give headroom and maintain accuracy. For example, a circuit with a 160A maximum demand would typically use a 200A CT.

You also need to check the meter accepts the secondary output of the CT. Most Owen Brothers meters are designed for standard 5A or 1A secondary output, or millivolt output depending on the model. If you are not sure, call the team on +44 (0) 161 624 6211 and they can confirm the correct specification.

How long have Owen Brothers been supplying energy meters in the UK?

Owen Brothers have been supplying electrical metering products from Oldham, Greater Manchester since 1953. The company manufactures its own OB range of meters and also distributes complementary products for commercial, industrial, and landlord applications.

Customers include electrical contractors, M&E engineers, commercial landlords, energy companies, and facilities management teams across the UK and internationally.

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