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CWT Ultra-Miniature

Wideband current probe for ac current measurement

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.

CWT Ultra Miniature Wideband Current Probe
Sense coil thickness 1.7mm
  • 1.7mm dia sense coils will fit between thelegs 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
Ultra-Mini current sense coil and ferrule
Ultra mini current sense coil and ferrule dimensions
T0220 Device
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

Selection table for CWT Ultra mini current probes

CWT Ultra Mini specifications
Type Sensitivity
(mV/A)
Peak current
(A)
Peak di/dt
(kA/uS)
Noise max*1
mV pk-pk
Droop
typ.
(%/ ms)
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 10.0 600 40.0 10 6.0 6.2 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

*1Distributed around the fL (3dB) bandwidth.

*2The high frequency bandwidth is in part dependent on coil length. Contact Powertek for values of fH for other coil lengths.

TYPICAL ACCURACY
(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/µs)

(value must not be exceeded)
PEAK 70.0
All models
1.0kA/uS (1.2kA/uS for CWT1 and above)
Coil and cable
COIL CIRCUMFERENCE ‘A’ (mm)
80mm
COIL CROSS SECTION ‘B’ (mm)
1.7mm
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 (℃)
-40℃ to +125 ℃ (coil)

For de-rating due to temperature cycling please consult Powertek

CABLE LENGTH (metre) (from box to coil)
1m
Power input - mechanical - environmental
Power Supply
All CWT units are supplied with four AA batteries (typical life 90 hours) and a 12V-24Vdc input socket and a power adapter 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)
TEMPERATURE RANGE (℃)
0℃ to +40℃
Ordering
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 1 80

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.