CT Clamp for Buss Bar vs Service Cable


I have a 200 Amp panel in the US fed by twin busbars, not service cables. As the busbars are quite wide, the standard CTs will not work. I have an Emporia Energy system that uses a different style CT for busbars. Would these work with the emonTXv4?
Or is there another model of CT that you would recommend?

Emporia Vue 200A flexible Current Sensors for Smart Home Device Energy – Emporia Energy

Here is a picture of these CTs installed on busbars.

Thank you,


The web page you linked to says they are only good for the Emporia kit, but on a linked page Emporia Technical Specs it shows a standard c.t but by implication the Rogowski coil is a direct substitute with the same 0.333 V output as required by the emonTx4. If so,
the answer looks to be yes, provided the correct connections are made on the plug - and the 12 V supply to the integrator does NOT come through this, which from the other picture it doesn’t. But if it does, you’ll need to make some arrangements to find a separate 12 V d.c. supply. And bear in mind to my knowledge, one has never been tested with the emonTx4, so there’s no guarantee either that it will work or that it won’t be damaged by or cause damage to the emonTx4 or the connected emonVs.

Note: You need to be very careful with your wording when you write busbar and clamp, because a busbar clamp is a temporary means of connecting a cable onto a busbar, one of the reasons I refuse to call a split-core c.t. a “clamp” - because it isn’t. “Clamp” seems to be a sloppy translation by the Chinese; in English until recently, the word has only ever been used to describe a clamp ammeter, which normally has spring-loaded jaws.

1 Like

Hi Robert,

I did find a similar flexible CT without the 12v supply - do you think this one would work?

Qtmnekly 2000V/Rms AC Leakage Current Sensor Multi-Functional Flexible Coil Current Sensor 0.1Hz - 1MHz ETCR100F - Walmart.com

Item Type: Current Sensor
Measuring Range: 10A-10000A-Higher
Resolution: 10mA
Grade: ±0.1% (50Hz / 60Hz; 23 ℃ ± 2 ℃, Relative Humidity 70%, The wire is in the middle of the coil)
Phase Error: ≤0.1° (50Hz / 60Hz; 23℃±2℃)
Output Interface: 3.5mm Plug
Output Line: 2m / 6.6ft
Current Frequency: 45Hz-70Hz (Measured Frequency)
Response Frequency: 0.1Hz - 1MHz
Line Voltage: AC1000V Line Test
Working Temperature and Humidity: -20 ℃ - 50 ℃; Relative Humidity 80%
Storage Temperature and Humidity: -10 ℃ - 60 ℃; Relative Humidity 70%
Dielectric Strength: 2000V / Rms AC (Both ends of the coil)
Function: Detecting of AC leakage current, AC big current, high harmonic current, complex waveforms current, inrush transient current, phase, electric energy, power, power factor.
Testing : Flexible CT: The output signal is the derivative of the current with to time, the input current can be truly restored by integrating the output voltage signal.
Material: plastic+metal
colour: As shown

Package Contents:
1 x Current Sensor

Only the above package content, other products are not included.
Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.

    1. It is small in size, light in weight, exquisite in appearance, soft and flexible, suitable for narrow environment and flat cable dense place.
    1. It is widely used in electric power, communication, meteorology, railway, oil field, architecture, measurement research and teaching units, industrial and mining enterprises and other fields.
  • Feature: 1. There is no exposed metal conductor in the coil, adopt non-contact measurement , which is safe and reliable.
    1. Wide measurement range, high accuracy, strong reliability, the hysteresis effect is not affected by the external electric field, and has a noise free frequency band (0.1 Hz-1 MHz).The position of the wire is located in the center of the test wire coil, and the influence of position error is less than 0.3% .
    1. It can detect AC leakage current, current, high-order harmonic current, complex wave current, transient pulse current, phase, power, power factor, etc.

Where is the integrator you need:

It’s not inside your emonTx4 and the processor is too busy to be able to add a software integrator.

I think you need to read up a bit about Rogowski coils. Rogowski coil - Wikipedia
From this:
“Since the voltage that is induced in the coil is proportional to the rate of change (derivative) of current in the straight conductor, the output of the Rogowski coil is usually connected to an electrical (or electronic) integrator circuit to provide an output signal that is proportional to the current.”
Aim Dynamics.What is Rogowski Coils and How Does it Work?
(Also a possible supplier.)

Robert, thank you for the link. Very helpful.
I plan on testing the Emporia CT clamps with the EmonTX and will advise if it works.

As I wrote, it should do, but…
The sleeve of the emonTx4 c.t. socket is connected to GND via the emonVs, so ideally the power supply to the Rogowski integrator will be floating and it will be grounded by the sleeve of the output jack plug. This is really the only problem you might encounter.
You will of course need to change the calibration constant to suit the 333 mV output at 200 A rather than at 100, 50 or 20 A.

Thx - will be installing and testing after Christmas.