CWTUM-S
Equipped with an extremely thin, clip-around coil (1.2mm cross-section).
This wide-band AC current probe is the thinnest clip-around Rogowski coil available from PEM, at just 1.2mm thickness it still achieves an insulation rating of 1.2kV peak.
Product Synopsis
CWTUM-S
Equipped with an extremely thin, clip-around coil (1.2mm cross-section).
The CWTUM-S is an even thinner version of the original CWT Ultra-mini probe from PEM. The Rogowski coil cross-section diameter is just 1.2mm without compromising operating temperature, high frequency performance or insulation voltage. Such a thin coil provides another solution for measuring current in tight spaces without disrupting the circuit under test.
A wide-band AC current probe with BNC output to connect to most types of oscilloscope or data acquisition devices.
Features
- Wide operating temperature -40°C to +125°C.
- High frequency (-3dB) 30MHz.
- Loads the circuit under test by only a few pH.
- Standard coil length (circumference) of 80mm.
- Coil insulation 1.2kV pk. 1.2mm cross section diameter.
- Peak di/dt capabilities up to 100kA/μs.
- Current ratings from 30A pk to 30kA pk.
Applications
- Switching current waveforms in power electronic circuits:
- MOSFET or IGBT devices as small as TO-220, D2PAK and other SMT power devices.
- Measuring power losses in semiconductor bond wires in power devices.
- Monitoring currents in small inductors, capacitors, snubber circuits, etc.
- Measuring small AC currents in the presence of large DC currents (e.g. monitoring capacitor ripple).
- Power converter development and diagnostics.
- Measuring high frequency sinusoidal, pulsed or transient currents in power frequency to rf applications.
Standards and Approvals
- 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
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
-
Wide operating temperature
Wide operating temperature -40°C to +125°C.
-
Wide-bandwidth
(-3dB) bandwidth from a few Hz to 30MHz.
-
Minimal insertion impedance
Loads the circuit under test by only a few pH.
-
Thin coils and high insulation
Coil insulation 1.2kV pk.
1.2mm cross section diameter.
Thinner coils available at lower insulation ratings. -
Peak di/dt
Peak di/dt capabilities up to 100kA/μs.
-
Current ratings
Current ratings from 30A pk to 30kA pk.
-
Customise cable length
Longer cables than the standard 1m are available on request.
-
Custom coil length
Coil lengths longer than the standard 80mm are available, up to 150mm.
-
Bespoke options
Choose from a range of standard options or create a custom design.
Performance
CWTUM-S
| Model | Sensitivity (mV/A) | Peak Current (A) | Noise(mVp-p) | Droop (%/ms) | LF (-3dB) (Hz) | Peak di/dt (kA/μs) | HF (-3dB) Bandwidth
(MHz)
|
|---|---|---|---|---|---|---|---|
| CWTUM-S/015 | 200 | 30 | 20 | 85 | 150 | 2.0 | 30 (80) |
| CWTUM-S/03 | 100 | 60 | 18 | 78 | 100 | 4.0 | 30 (80) |
| CWTUM-S/06 | 50 | 120 | 12 | 70 | 75 | 8.0 | 30 (80) |
| CWTUM-S/1 | 20 | 300 | 10 | 53 | 50 | 20 | 30 (80) |
| CWTUM-S/3 | 10 | 600 | 12 | 11 | 12 | 40 | 30 (80) |
| CWTUM-S/6 | 5.0 | 1200 | 12 | 5.5 | 6.0 | 80 | 30 (80) |
| CWTUM-S/15 | 2.0 | 3000 | 10 | 2.8 | 3.0 | 100 | 30 (80) |
| CWTUM-S/30 | 1.0 | 6000 | 10 | 1.5 | 1.5 | 100 | 30 (80) |
| CWTUM-S/60 | 0.5 | 12,000 | 8.0 | 1.0 | 1.0 | 100 | 30 (80) |
| CWTUM-S/150 | 0.2 | 30,000 | 5.0 | 1.0 | 1.0 | 100 | 30 (80) |
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 80mm coil, 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 |
|---|---|---|
| CWTUM-S | 100kA/μs | 1.0kA/μs |
Technical Specifications
CWT ultra-mini
- Output
-
±6V pk corresponding to ‘Peak Current’ into ≥ 100kΩ (recommended e.g. DC1MΩ oscilloscope).
±2V pk, Sensitivity is half the nominal value into 50Ω. - Accuracy
-
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
-
±3mV max. at 25°C
- Temperature
-
Coil and cable -40°C to +125°C
Integrator 0°C to +40°C - Coil voltage
-
1.2kV pk
Safe peak working voltage to earth.
Rating established by a 3kV rms, 50Hz, 60 sec flash test. - Cable length
-
1m (length of cable from coil to electronics).
(Longer cables are available on request). - Coil length
-
80mm
(Longer coils are available on request). - Battery Options
-
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
CWTUM-S Dimensions
Minimum Bend Radius
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
Longer coils are available on request.
What is included?
The CWTUM-S 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 CWTUM-S 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 CWTUM-S you can get a quote, if your requirement is outside that listed on our website please contact us to discuss your requirements and application.
-
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.
-
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).
-
Carry Case
Robust hard plastic carry case with handle to protect the CWT probe in transit. Dimensions: 330mm x 265mm x 58mm.
-
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).
-
Calibration Certificate
Every unit is supplied with a fully traceable calibration certificate.
Customise & Options
PEM can customise CWTUM-S 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.
-
Longer Cables
Longer cables are available up to 10m.
(Custom lengths available on request) -
Longer Coils
Longer coils are available up to 150mm.
(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.
-
Datasheets
XX21S and XX13S - Power Adaptor Technical Specification Datasheet PDF 575KB Updated: 20th November, 2024
-
Datasheets
CWTUM-S Datasheet PDF 1.3MB Updated: 12th November, 2024
-
Instruction Sheets
CWTUM / CWTUM-S Instruction Manual PDF 667KB Updated: 24th November, 2024
-
Dimension Drawings
CWTUM-S Dimensions PDF 592KB Updated: 4th June, 2024
-
CAD Files
CWTUM Enclosure STEP 29.0MB Updated: 23rd May, 2024
-
Technical Notes
High Frequency Performance and Rise-time PDF 1.5MB Updated: 20th November, 2024
-
Technical Notes
Voltage Immunity PDF 1.4MB Updated: 22nd October, 2024
-
Technical Notes
Low Frequency Performance - 01A PDF 1.6MB Updated: 22nd October, 2024
-
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.
-
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.
-
Double Pulse Testing
Double Pulse Testing
Fast Rogowski probes for dynamic power semiconductor testing in new SiC devices.The double pulse test is widely used to test the parameters of power MOSFETs and power IGBT’s. The circuit replicates the type of inductive load that is typical in power converter design. The test can be used to measure the semiconductor energy loss during switch on/off as well as the reverse recovery time of the diode.
The CWTMini50HF is the perfect choice for measuring the current flowing in modern power devices including SiC semiconductors. The 50MHz bandwidth is sufficient to measure a rise time of 12ns without distortion and the measurement delay is predictable and repeatable, which enables the user to correctly de-skew the current measurement and calculate energy loss.
The coil contains no magnetic materials and has a small cross section which minimises the inductance inserted in the primary circuit which could negatively affect the maximum achievable switching speed of the device being tested.
-
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.
-
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.
Compliance
We prioritise compliance with industry standards ensuring all products are safe.
Quality Standards
We are committed to delivering the highest standards of excellence to customers.