CWT Ultra miniature wideband current probe
for ac current measurement

UK Tel: +44 1788 519911
US Tel: +1 631 615 6279
Email :
Email :

return to homepage | | contact us

Click here for mobile friendly version page


The CWT ULTRA Miniature current probes utilize a Rogowski Coil current sensor thin enough (typical cross section 1.7mm) to fit between the legs of a T0220 semiconductor switching device. With a high frequency bandwidth up to 30MHz, the CWT ULTRA miniature is ideal for measuring steady state current, switching transients or pulsed currents between 300mA and 6000Apk in power electronic equipment. The CWT ULTRA miniature probe is a clip around flexible coil current probe, based on the Rogowski principle to achieve high bandwidth measurement and faithful conversion of current to voltage, intended for use with oscilloscopes, transient recorders, data loggers, power meters and power analyzers. All models are supplied with an 80mm length clip-around coil, ensuring easy current monitoring even where access is limited.

cwtultra.jpeg (7485 bytes)

Sense coil thickness 1.7mm

bullet 1.7mm dia sense coils will fit between the
legs of T0220 package

Very thin & flexible clip-around sense coil


Peak Current ratings from 30Apk to 6000Apk


Sensitivity set to give ▒ 6 volts peak
output(e.g. 20.0mV/A for ▒ 300A peak)


Capability of driving 50 ohm impedance


30MHz High Frequency Bandwidth


Accuracy typically 0.2% of reading


Sense coil length of 80mm


Peak voltage isolation 1.2kV


umferrule.jpg (16818 bytes)

Ultra mini current sense coil and ferrule dimensions


CWT Ultramini models and current ranges

  CWTUM/015/B/1/80 = 200mV/A 30A   order code CWTUM/015/B/1/80
  CWTUM/03/B/1/80 = 100mV/A 60A   order code CWTUM/03/B/1/80
  CWTUM/06/B/1/80 = 50mV/A 120A   order code CWTUM/06/B/1/80
  CWTUM/1/B/1/80 = 20mV/A 300A   order code CWTUM/1/B/1/80
  CWTUM/3/B/1/80 = 10mV/A 600A   order code CWTUM/3/B/1/80
  CWTUM/6/B/1/80 = 5.0mV/A 1200A   order code CWTUM/6/B/1/80
  CWTUM/15/B/1/80 = 2.0mV/A 3000A   order code CWTUM/15/B/1/8
  CWTUM/30/B/1/80 = 1.0mV/A 6000A   order code CWTUM/30/B/1/80

Cable length - The cable connecting the measurement coil to the integrator box is 1m


CWT Ultra mini datasheet pdf | CWT Ultra Mini user manual

Selection table for CWT Ultra mini current probes

CWT Ultra Mini specifications

Type Sensitivity


Peak current


Peak di/dt


Noise max*1





LF (3dB) bandwidth typ. (Hz) fL Phase lead at 1kHz

typ. (deg)

HF (3dB) bandwidth typ. (MHz) fH *2
Coil Length 80mm
High Sensitivity Ranges of CWT .... measuring currents from 300mA
CWT015 200.0 30 2.0 20 80 116 8.4 30
CWT03 100.0 60 4.0 20 65 67 4.2 30
CWT06 50.0 120 8.0 15 35 34 2.1 30
CWT1 20.0 300 20.0 15 9.0 9.2 0.7 30
CWT3 10.0 600 40.0 10 6.0 6.2 0.7 30
CWT6 5.0 1200 70.0 10 3.0 3.2 0.7 30
CWT15 2.0 3000 70.0 5.0 2.0 2.0 0.7 30
CWT30 1.0 6000 70.0 5.0 2.0 2.0 0.7 30

*1. Distributed around the fL (3dB) bandwidth. 
*2. The high frequency bandwidth is in part dependent on coil length.   Contact Powertek for values of fH for other coil lengths. 


(full scale)

Calibrated to UKAS ▒0.2% with conductor central in the loop

Variation with conductor position in the coil loop typically ▒2%

TYPICAL LINEARITY ▒0.05% (full scale)
di/dt ratings
Absolute maximum values of di / dt (kA/Ás)

(value must not be exceeded)

PEAK  70.0
All models
1.0kA/uS (1.2kA/uS for CWT1 and above)

Coil and cable

PEAK COIL VOLTAGE ISOLATION (kV) 1200V rating established by a 3kVrms, 50Hz, 60sec flash test
Safe peak working voltage to earth. Coils are flash tested at 3kV/60Hz for 60 seconds.  Information about the continuous use of coils at high voltage can be obtained from Powertek
TEMPERATURE RANGE (oC) -40oC to +125 oC (coil)
For de-rating due to temperature cycling please consult Powertek
CABLE LENGTH (metres) (from box to coil) 1m   


Power input - mechanical - environmental


All CWT Ultra Mini units are supplied with four AA batteries (typical life 90 hours) and a 12V-24Vdc input socket and a power adapters to power the CWT from 230Vac or 115Vac.  Specify adapter type, 230Vac  or 115 Vac
INTEGRATOR BOX DIMENSIONS (mm) H =183mm, W = 93mm, D = 32mm
OUTPUT SOCKET BNC (output impedance 50 ohms- unit supplied with 0.5m BNC-BNC coaxial cable)
MIN. OUTPUT LOADING >100kohm (for rated accuracy).  50ohm will reduce the sensitivity to half its normal value (for driving long cables >10m)



Model / sensitivity
CWT Ultra mini unit is supplied with bnc-bnc cable, 12-24Vdc input, 4 AA batteries, power adapter, user manual, calibration certificate and carry case.  
Range / Model / Denotes battery / Cable length (m) / Coil circumference (mm)
CWT UM / 015 / B /




All CWT current probes are supplied with hard carry case, bnc-bnc cable, batteries, power adapter, user manual,
statement of conformance & calibration certificate

If you have any queries regarding the CWT Ultra Mini or require specifications outside our standard ranges please do not hesitate to contact us


CWT Ultra mini datasheet pdf | CWT Ultra Mini user manual

CE marked

Return to Homepage