Rogowski Coils: Product List Rocoil Logo 
 A complete current measuring system normally consists of a coil and an integrator. Coils and integrators are usually provided separately. This allows a greater degree of flexibility in designing measuring systems. Also it allows coils to be supplied separately for people who want to use their own electronics.

At present all equipment supplied by Rocoil is manufactured as ordered. Because of the large variety of options it is not practicable to keep items ‘on the shelf’. In many cases we can incorporate individual customer preferences, such as a special frequency response characteristic, at no extra cost.

Flexible Coils 
Rigid Coils
Type 8000 Transducers

Rail Current Transducers
High-Frequency Coils


We supply flexible coils in lengths up to several metres, with or without screens and in a variety of finishes. NOTE: flexible coils are specified by their length and not by the size of the conductor that they will enclose.

FLEXIBLE COILS WITH 'BUTTED-TOGETHER' ENDS: With the Type 1000 series the ends of the coil are 'butted' together and an additional coil is fitted near the join to compensate for the gap in the winding. They are wound with various wire sizes giving mutual inductance values in the range 0.2 - 0.3 micro Henries. These coils are provided with either push-together ends or screw-together ends. (See Flexible Rogowski Coils for more details.) The coils are normally provided with a 2m long output lead (twisted pair with overall screen) but longer leads up to at least 100m can be fitted.

Type 1012: Flexible coil, no screen, with 2 layers of insulation comprising a coloured inner layer covered by a tough grey/black outer layer. Cross-sectional diameter approximately10mm


Type 1112: Flexible coil which incorporates an electrostatic screen. Insulation over the screen consists of a coloured inner layer with a tough grey/black outer layer. Cross-sectional diameter approximately 12mm.

Type 1022: Small cross-section coil, (approximately 6mm diameter), unscreened double insulated

Type 1122: Small cross-section coil, (approximately 7mm diameter)), screened and double insulated

Type 1232: Low Output coil: A screened coil used where the rate of change of current is very large to ensure that the voltage developed in the coil is not excessive. Cross-sectional diameter approximately 7.5mm.

FLEXIBLE COILS WITH OVERLAPPING ENDS: With these coils the ends are overlapped to align the ends of the winding. In some cases the cross-talk from stray magnetic fields is not as good as for the type 1000 series coils. the 4000 series uses a simple clip to align the ends. Robinson coils use a Velcro strip.

Type 4022: Small cross-section coil, (approximately 6mm diameter), unscreened.

Type 4022/NC: Similar to the 4022 but with cable-tie fixing for long-term installations.

Type 545: This is specifically designed to be compatible with the Robinson type 543 integrator. The construction is similar to the Type 1120 but the coil ends are overlapped, as with the original Robinson 545, rather than butted together and the outer layer of insulation is a polyester braid. The coil is fitted with a termination box. NOTE: Type 1000series coils can also be built with a termination box to be compatible with the Robinson integrator.

Type 4022 coil
  Type 4022 coil: click on the picture for an enlargement 

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2) RIGID COILS (Type 2000 Series)

 Dimensions and characteristics of some standard rigid coil sizes are given on a separate page. (See Rigid Rogowski Coils) We can vary the characteristics by using different wire sizes for the winding. We can also suppiy rigid coils for use with the Robinson type 543 integrator.

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We design and build integrators for use with any of the flexible or rigid coils except for the 545. The normal output from an integrator is a voltage which reproduces the current wave-form. The sensitivity is defined as the current which gives a 1V output (amps/volt). The output is linear up to 5 or 10 V depending on the type. Standard sensitivity ranges are:

100A, 1kA, 10kA and 100kA for flexible coils; 10A, 100A, 1kA and 10kA for rigid coils.

We can supply sensitivities at any intermediate ranges within these limits. We can also supply sensitivities outside these limits but for lower currents this may result in a restricted low-frequency performance and a noisier output.

Coil outputs can vary even between coils iof nominally the same design. Consequently integrators are supplied matched to individual coils. We also have an interchangeable where any coil can be used with any integrator.

Type SIPCB: A single integrator on a PCB with two sensitivity ranges, suitable for OEM use. Connections to the board (coil input, output, power) are via a screw terminal strip. The board requires positive and negative supplies which can be up to +/-18V DC. Board dimensions are approximately 50mm x 50mm. Picture of SIPCB

Type 6140: A single-channel integrator in a hand-held box, powered by two PP3 batteries. 1V for full scale output with 5x over-range capability. Four ranges selected by a switch.

Type 7141: A single-channel bench-top integrator with a mains/battery power supply having a rechargeable battery. 1V for full-scale output with 10 x over-range capability. Four ranges, selected by a switch. Mains supply 110 - 240V

Type 7341: A three-channel bench-top integrator with a mains/battery power supply having a rechargeable battery. 1V for full-scale output with 10 x over-range capability. Four ranges, selected by a switch. Mains supply 110 - 240V. Picture of type 7341

Passive: Passive integrators are sometimes preferred for monitoring large, fast current pulses.

Module: Integrators can be supplied as rack-mounted modules with 1, 2 or 3 channels per module. The modules are designed according to customer requirements.

Wall-Mounted: Multi - channel integrators in a steel wall-mounted enclosure suitable for permanent installation having IP66 protection. Built-in mains power supply. These integrators normally have only one sensitivity which is specified by the customer. They normally have a current-waveform output. The 'Wallmount' version has a 14mA RMS (20mA peak) output. The 'Oneamp' integrator has a 1 Amp RMS waveform output and is intended as a replacement for a CT.

DIN-Rail Mounted: The 'DIN1' integrator has a 4 - 20mA output using a two-terminal connection; The DINAC integrator has an analogue voltage waveform output. Picture of DIN-Rail integrators

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RMS Output: An additional DC output for each channel equal to the true rms value of the AC output. (not available with SIPCB or passive versions)

Overload: An indicator for each channel which lights when the output voltage is close to the maximum for the integrator. With a transient overload the light will remain on for about 1 second. (not available with SIPCB or passive versions)

Sum: An output at the rear of the integrator which provides an instantaneous sum of the three AC outputs. Each channel has a sum switch which can be set to +, 0, or - depending on whether the channel output is to be added to the sum, not included or subtracted. (Type 7300 only)

Current Driver: A current output representing the current wave form. Normally ± 20mA for the maximum output of the integrator (10V). This option is mainly for use with permanent installations.

Low Frequency Options: The low frequency rolloff is normally set to be -3dB at about 1Hz. Some applications require a different rolloff, for example a lower frequency for transient measurements or a higher frequency when it is necessary to suppress some frequencies. In many cases these variations can be provided.

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4) TYPE 8000 Transducers

The Type 8000 is a complete transducer (coil + integrator) which has been designed mainly for use at power frequencies. It features a very low power consumption lasting for up to 12 months continuous use on a single alkaline PP3 battery. The '12 month' option has a bandwidth up to 2.5kHz. Higher frequency versions can be supplied but at the expense of increased battery drain. This unit is normally equipped with a coil type 1012 length 0.5m but longer coils can be fitted.

Type 8112: Single range version in a plastic box

Type 8132: Three range version (illustrated)
 Type 8000 Integrator
  More details on the Type 8000: PDF file,  55KB click on the picture to enlarge it


These are designed to measure the currents in railway lines without the need to totally encircle the rail which would be necessary with a flexible coil. They mount over the top of the rail. They were developed for measuring track circuit signalling currents. The output is a voltage reproducing the current wave-form which can be displayed on a multimeter or oscilloscope or used in conjunction with a spectrum analyser.

'Version 1 (illustrated) has a frequency response which is flat from 20Hz to above 33kHz. The sensitivity is 10A/V with a maximum current capability up to 50A. A spectrum analyser is has been built specially for use with this instrument by Ultrasound Advice, UK.

Version 2 has been developed for main-line circuits which has a built-in 50Hz rejection filter. This allows track-circuit currents to be measured when large traction currents are flowing. More Details of Version 2
 Rail Current Transducer


We can supply a range of high-frequency coils suitable for measuring RF current pulses and Continuous Wave currents up to about 100MHz and having a rise-time of about 3nS. These coils are of the self-integrating type and so do not require additional integrators. They are designed to operate directly into equipment having an input impedance of 50W. These coils were originally designed for discharge monitoring of insulation and they all have excellent rejection of power frequency currents. Low frequency (-3dB) bandwidths are in the range 2.5kHz to 100kHz depending on the design.

Several of these designs are suitable for use in intrinsically safe applications. These coils are manufactured by Exon Consultancy and technical queries should be directed to them.

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