CWTMini
A wide-band AC current probe, with a small clip- around Rogowski coil. Ideal for power measurements and harmonic analysis.
A wide-band AC current probe with a small coil enabling measurement in even the most difficult to reach parts of a circuit.
Product Synopsis
CWT Mini
A wide-band AC current probe with a small coil enabling measurement in even the most difficult to reach parts of a circuit.
The CWTMini has a small clip around coil and wide bandwidth making it useful in applications as diverse as power frequency and harmonic current analysis to measuring long duration pulses. The small coil is offered in two insulation voltages 2kV peak, 3.5mm cross section diameter and 5kV peak, 4.5mm.
Key Features
- Extended low frequency performance.
- Predictable phase response from Hz to > 100kHz.
- Low droop distortion for measuring longer pulses.
- High frequency operation into MHz.
- Current ratings from 60A pk to 300kA pk.
- Standard coil length (circumference) of 100mm or 200mm.
- Thin coils 3.5mm cross section diameter for a 2kV pk insulation and 4.5mm for a 5kV pk coil.
Applications
- Power frequency 50/60Hz measurements and higher order harmonics
- Pulsed currents, and pulsed power measurements with longer duration pulses.
- Measuring small AC currents in the presence of large DC currents (e.g. monitoring capacitor ripple).
- Power converter development and diagnostics.
- Measuring currents in difficult to reach conductors such a tightly packed bus-bars.
- Power quality monitoring in variable speed drives, UPS, power systems or SMPS circuits
Standards and Compliance
- CE marked
- Complies with EMC EN61326-1
- Complies with IEC 61010-1; IEC 61010-2-032
- PEM Ltd is certified to the ISO9001:2015 standard
- Patented product
PEM are committed to delivering the highest level of quality to our customers, read more about how we strive to achieve this in our Quality Standards and Compliance sections.
Key Features
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Enhanced Performance
Extended low frequency performance.
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Low droop distortion
Low droop distortion for measuring longer pulses.
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Wide-bandwidth
High frequency operation into MHz.
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Current ratings
Current ratings from 60A pk to 300kA pk.
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Thin coils and high insulation
Thin coils 3.5mm cross section diameter for a 2kV pk insulation and 4.5mm for a 5kV pk coil.
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Customise cable length
Longer cables than the standard 1m, 2.5m and 4m are available on request.
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Custom coil length
Coil lengths longer than the standard 100mm and 200mm are available, even coils > 1000mm.
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Bespoke options
Choose from a range of standard options or create a custom design.
Performance
CWTMini
| Model | Sensitivity (mV/A) | Peak Current (A) | Noise(mVp-p) | Droop (%/ms) | LF (-3dB) (Hz) | Peak di/dt (kA/μs) | HF (-3dB) Bandwidth
(MHz)
|
|---|---|---|---|---|---|---|---|
| CWTMini/03 | 100 | 60 | 15 | 6.6 | 7.0 | 1.0 | 10 (100) |
| CWTMini/06 | 50 | 120 | 15 | 4.8 | 5.0 | 2.0 | 10 (100) |
| CWTMini/1 | 20 | 300 | 12 | 3.6 | 4.0 | 2.5 | 20 (100) |
| CWTMini/3 | 10 | 600 | 10 | 1.8 | 2.0 | 5.0 | 20 (100) |
| CWTMini/6 | 5.0 | 1,200 | 10 | 0.8 | 0.9 | 25 | 20 (100) |
| CWTMini/15 | 2.0 | 3,000 | 8.0 | 0.4 | 0.5 | 25 | 20 (100) |
| CWTMini/30 | 1.0 | 6,000 | 7.0 | 0.25 | 0.3 | 40 | 20 (100) |
| CWTMini/60 | 0.5 | 12,000 | 5.0 | 0.2 | 0.2 | 40 | 20 (100) |
| CWTMini/150 | 0.2 | 30,000 | 5.0 | 0.1 | 0.1 | 40 | 20 (100) |
| CWTMini/300 | 0.1 | 60,000 | 5.0 | 0.05 | 0.05 | 40 | 20 (100) |
| CWTMini/600 | 0.05 | 120,000 | 5.0 | 0.03 | 0.02 | 40 | 20 (100) |
| CWTMini/1500 | 0.02 | 300,000 | 5.0 | 0.03 | 0.02 | 40 | 20 (100) |
Noise - ‘Noise’ is the internally generated integrator noise, this is predominantly the same frequency as the LF (-3dB) bandwidth.
HF (-3dB) Bandwidth - The HF(-3dB) is specified for a 1m cable and either a 100mm coil or 200mm coil as indicated, we can supply longer coils and cables on request.
di/dt ratings
These are ‘Absolute maximum di/dt ratings’ and values must not be exceeded.
| Type | Abs. Max. peak di/dt | Abs. Max. rms di/dt |
|---|---|---|
| CWTMini | 40kA/μs | 1.0kA/μs |
Technical Specifications
CWTMini
- Output
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±6V pk corresponding to ‘Peak Current’ into ≥ 100kΩ (recommended e.g. DC1MΩ oscilloscope).
±2V pk, Sensitivity is half the nominal value into = 50Ω. - Accuracy
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Calibrated to ±0.2% reading with conductor central in the Rogowski coil loop.
Conductor position in the coil (for a 2mm dia. conductor) typically ±2% reading.
Conductor position in the coil (for a 10mm dia. conductor) typically ±1% reading.
Linearity (with current magnitude) 0.05% reading. - DC offset
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±3mV max. at 25°C
- Temperature
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Coil and cable -20°C to +100°C
Integrator electronics 0°C to +40°C - Coil voltage
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2kV pk (3.5mm thick coil).
5kV pk (4.5mm thick coil).
Safe peak working voltage to earth. - Cable length
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1m, 2.5m or 4m (length of cable from coil to electronics).
(Longer cables are available on request). - Coil length
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100mm or 200mm.
(Longer coils are available on request). - Battery Options
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BAlkaline Batteries -- 4 x 1.5V AA alkaline batteries.
External power adaptor disconnects batteries and powers unit.RRechargeable Batteries -- 4 x 1.2V NiMH batteries.
External power adaptor trickle charges batteries and powers unit.External power adaptor available in US, EURO, UK & AUS versions as an optional extra.
Dimensions
CWTMini / CWTMini50HF 2kV Dimensions
Standard Coil Lengths
200mm
Longer coils are available on request.
Coil Length and Sizing Guide
As a general 'guide to sizing' the coil, it will fit a circular conductor with a maximum diameter
= [Coil length / 3.3]
Minimum Bend Radius
13mm, CWTMini
CWTMini / CWTMini50HF 5kV Dimensions
Coil Length and Sizing Guide
As a general 'guide to sizing' the coil, it will fit a circular conductor with a maximum diameter
= [Coil length / 3.3]
Standard Coil Lengths
200mm
Longer coils are available on request.
Minimum Bend Radius
13mm, CWTMini
What is included?
The CWTMini is supplied with some standard items so your measurement is ready to go the moment you receive your probe.
Details of how to specify a CWTMini probe including peak current rating, coil circumference, cable length and the type of batteries to power the electronic integrator can be found in the performance section.
If you want to purchase a CWTMini you can get a quote, if your requirement is outside that listed on our website please contact us to discuss your requirements and application.
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CWT Probe
Clip-around Rogowski coil, with cable connected to an electronic integrator housed in a plastic enclosure. The enclosure has an output BNC socket, ON/OFF switch, slide panel for batteries and socket for external DC power.
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0.5m BNC Output Cable
Every CWT unit is supplied with a detachable 50ohm BNC to BNC output cable. (The CWTMini50HF output cable is fixed).
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Carry Case
Robust hard plastic carry case with handle to protect the CWT probe in transit. Dimensions: 330mm x 265mm x 58mm.
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Batteries
Choose from either (4 x 1.5V Alkaline) or (4 x 1.2V NiMH) Rechargeable AA Batteries. (The CWT has trickle charge capability for the NiMH battery option).
Customise & Options
PEM can customise CWTMini current probes, and supply optional items, that may be required for your specific measurement.
Customisation can be as simple as choosing coil lengths or cable lengths outside those specified on the datasheet, or you may have more complex requirements, see custom designs for some examples.
Additional optional items for the CWT range include a low noise wall mount power adaptor.
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Longer Cables
Longer cables are available up to 10m.
(Custom lengths available on request) -
Longer Coils
Longer coils are available, even coils > 1000mm
(Custom lengths available on request) -
Power Adaptor
External power adaptor available in US, EURO, UK & AUS versions as an optional extra.
Get a Quote
Build your CWT product options and complete our online quotation form.
Custom Design
We can provide custom designs for one off applications or volume manufacture.
Downloads
For more information and documents please see our full technical resources area.
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Datasheets
XX21S and XX13S - Power Adaptor Technical Specification Datasheet PDF 575KB Updated: 20th November, 2024
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Datasheets
CWTMini Datasheet PDF 1.7MB Updated: 12th November, 2024
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Instruction Sheets
CWTMini Instruction Manual PDF 664KB Updated: 20th November, 2024
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Dimension Drawings
CWTMini / CWTMini50HF 5kV Dimensions PDF 816KB Updated: 26th May, 2024
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Dimension Drawings
CWTMini / CWTMini50HF 2kV Dimensions PDF 637KB Updated: 26th May, 2024
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CAD Files
CWTMini / CWTMini50HF Enclosure STEP 30.6MB Updated: 23rd May, 2024
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CAD Files
CWTMini / CWTMini50HF Coil 5kV STEP 2.7MB Updated: 23rd May, 2024
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CAD Files
CWTMini / CWTMini50HF Coil 2kV STEP 2.5MB Updated: 23rd May, 2024
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Technical Notes
High Frequency Performance and Rise-time PDF 1.5MB Updated: 20th November, 2024
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Technical Notes
Low Frequency Performance - 01A PDF 1.6MB Updated: 22nd October, 2024
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Compliance
CWT / LFR / CMC / DCFlex Warranty PDF 197KB Updated: 9th January, 2025
Technical Resources
Browse our extensive resources of technical information, insights and test data.
Get a Quote
Build your CWT product options and complete our online quotation form.
Applications
For more information on possible and suitable applications please review the applications below and click each one for further information.
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EMC Applications
EMC Applications
The wide-band CWT range is a versatile tool in EMC measurement applications.The CWT range has been used in a wide variety of EMC applications. It has a wide-bandwidth from sub Hz into the MHz range and configurable current ranges from less than 1A to >100kA.
Two examples demonstrate the versatility:
- The CWT has been used as the reference measurement in EMC magnetic impulse immunity testing where the DUT has to continue operation in the presence of a local impulse for several kA
- The CWT has also been used in many EMC traction applications where a measurement of mA level currents at frequencies > 1kHz need to be resolved in the presence of large 16.6 or 50/60Hz currents.
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Large AC Currents
Large AC Currents
Ideal for large AC currents in generators, motor drives and power supplies.Unlike other forms of current measurement the size of the sense coil (the Rogowski coil) is independent of the size of the measured current. Thus for large currents the size of the Rogowski coil can be chosen to suit the conductor diameter, whereas probes based on magnetic materials such as hall effect become increasingly bulky and expensive at larger current ratings.
Over a 1000A range there really is no better alternative to a PEM Rogowski current probe.
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Small AC on Large DC Currents
Small AC on Large DC Currents
Examples including measuring small ripple currents on a large magnitude DC bus.Rogowski current probes do not measure the DC component of a current. However unlike a current transformer or a fluxgate device they contain no magnetic materials so are unaffected by the DC current. Therefore it is possible to use a small, flexible, Rogowski coil to measure a small AC current in the presence of a large DC current, whereas a sensor based on a magnetic principle would be expensive and bulky to prevent saturation effects. One such common application is measuring the ripple current in capacitors where the main current is DC or slow time varying.
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Power Electronics Diagnostics
Power Electronics Diagnostics
Thin, flexible, clip-around and wide-bandwidth, an ideal probe for measuring in power converters.The CWT can be used for a wide variety of power converter measurements such as switching loss in power semiconductors, capacitor ripple, or checking that in-circuit inductance is not over stressing an IGBT or MOSFET.
The CWT range is non-intrusive injecting only a few pH into the primary circuit, it has a high frequency bandwidth of up to 50MHz, a predictable known measurement delay, versions to mitigate interference from fast voltage transients, and comes in a variety of thin and clip-around coils with different isolation voltages, making it easy to insert into even difficult to reach parts of the circuit.
Quality Standards
We are committed to delivering the highest standards of excellence to customers.
Compliance
We prioritise compliance with industry standards ensuring all products are safe.