Regular CT Cons

Current transformers (CTs), sometimes also called current sensors, industry standard versions commonly have 5A as its output. They have the following disadvantages when used in branch circuits.

Regular CTs are large

Regular CTs are large and will occupy a lot of space in a panel.

Regular CTs need multiple windings

Branch circuit loads often do not exceed 75A, but since regular CTs have poor accuracy, they need to be wound multiple times to compensate.

Hard to install

During retrofitting, the existing layout and wiring constrains any new additions, since regular CTs are large, it is often difficult if not impossible to fit them.

Why the Need?

Regular CTs won't fit in existing panels

But dedicated CTs are small enough to fit.

When high accuracy is needed

Dedicated CTs can be as accuracte as 0.3%, much better than the 1% of regular CTs.

Installing a CT w/o interrupting power

Split core CTs can be used, they can be installed easily w/o lengthy disruptions, reducing both time and effort.

Same circuit, but branching wiring

Small CTs allow for parallel connections.

CT Types

A visual comparison of regular CTs with our dedicated CTs, both solid and split core.

CT image comparison

Size Comparison

Regular vs Dedicated CT

Various CT Size Comparison


Installing in a new panel

New Panel

Since dedicated CTs are small, they demand much less space when placed in new panels, as such the panels needed can be much smaller than normal. They are also low cost and aesthetically pleasing.


Existing Panel Retrofit

When an existing panel needs to be metered, CTs are absolutely required. But since space is cramped, regular CTs will not fit in between the wires, whereas dedicated CTs are small enough to fit.

Regular Split Body

Outer Dimensions (W x H x D) Window Dimensions (A x B)
114 x 145 x 32 mm 50 x 80 mm

When doing temporary testing or when demands require that the power cannot be interrupted, then the regular split body type of CT is ideal. They are available with various capacities including 100A, 200A, 300A and 600A. They are all regular 5A output and can thus be used with any meter that accepts 5A as its CT input.

pdf download Regular CT Datasheet

Regular Split Core

Regular split core CT
Current Rating Outer Dimensions
(W x H x D)
Window Dimensions
(A x B)
100A / 200A 51 x 67 x 34 mm 24 x 24 mm
400A 68 x 85 x 42 mm 36 x 37 mm

For existing panels that need to be retrofitted with meters, the space is sometimes simply too cramped to accommodate regular CTs due to their large size, but our regular split core CTs are only about half the size and can often fit within the space of existing panels; in addition, they can be installed without even having to interrupt the power or changing the wiring. Their output is 1A instead of 5A, they are available in 100A, 200A or 300A capacities.

pdf download Regular CT datasheet

Dedicated Solid Core

Our dedicated CTs are specific to our panel meters and the SMB350.
Small dedicated solid core CTs

Existing panels are too cramped for regular CTs, but our dedicated CTs are only about a third of their size and often small enough to fit. They are available in 5A, 50A and 200A capacities.

CT windings comparison for regular and dedicated CTs

Regular CTs have poor accuracies and often need multiple windings to compensate, but our dedicated CTs are accurate enough that do not require it.

Dedicated Split Core

Dedicated Split Core CTs

Sometimes it is necessary to meter an existing panel, but often the allowable space is too small for regular CTs, and to compound the problem, the power cannot be cut off even during installation. The solution is to use our dedicated split core CTs, not only are they about a third of the size and small enough to fit in existing panels, but they can be split open and simply snapped onto the wire during installation. Their accuracy is also very high compared to other split core CTs.

Model # Current Rating Outer Dimensions
(W x H x D)
Window Dimensions
(A x B)
CT-5S 5A 25 x 41 x 33 mm 10 mm
CT-50S 50A 26 x 48 x 23 mm 10 mm
CT-100S 100A 31 x 54 x 30 mm 16 mm
CT-200S 200A 36 x 76 x 45 mm 24 mm
CT-400S 400A 60 x 80 x 40 mm 35 mm
CT-600S 600A 60 x 80 x 40 mm 35 mm
CT-50SB 50A 23 x 39 x 26 mm 10 x 10 mm
CT-100SB 100A 32 x 56 x 31 mm 16 x 16 mm
CT-200SB 200A 51 x 67 x 34 mm 24 x 24 mm

pdf download Dedicated CT datasheet