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CWT / CWT LF Clamp on Current Probes

Wideband Clamp On Current Probes

The CWT current sensors are rugged clip around flexible coil wideband clamp on current probes, using Rogowski Coil technology for wide bandwidth measurement and faithful conversion of current to voltage, intended for use with oscilloscopes, data loggers, transient recorders, power meters and power analyzers - ideally suited for power electronic applications. Based on the Rogowski principle, these probes have intrinsic high bandwidth performance allowing measurement of both small and large currents (1A-600kA) from 0.01Hz to 20MHz. The small coil profile (8mm dia), means the coil can be retrospectively installed without disruption to active power systems. As standard, the coil is insulated at 10kVrms, insulation can be increased if required. Models are available with a variety of clip-around coil sizes to suit most conductors, allowing easy current monitoring even where access is limited.

clamp on current probes
clamp on current probes
  • Bandwidth 1Hz to 16 MHz (see bandwidth spec for each model)
  • CWT LF models available with extended LF bandwidth <1Hz
  • Models covering a 1A - 600,000Amps range
  • 0.2% accuracy
  • 10kV Insulation capability
  • Optional Electrostatic screens
  • Flexible "clip-around" coil
  • ±6V Instantaneous isolated output ideal for scopes, data loggers, PCI DAC cards and power analyzers
  • Uses 4 x AA batteries or 12V ac adapter (110V or 230Vac)
  • Traceable calibration certificate included
  • CE marked
  • Wide variety of models in stock

Application

Typical uses

Power analyzers
Convenient method of extending the current, power and harmonic measurement range without bandwidth degradation. Excellent low frequency (0.5Hz) performance along with low phase shift
Motor drives and power electronic converters
Allows measurement of IGBT switching times, gate turn on / turn off times and peak current
Motors and generator
Easy retrospective installation of probes around conductors where regular clamp and split core CTs are unsuitable
Induction heating
Measurement of high current / high frequency signals, including high order harmonic effects
Pulsed current applications
Semiconductor switches: IGBT, Power MOSfets, capacitor discharge and circuit breaker interruption currents
Capacitor discharge and lightning strike research
Measurement of peak currents without breaking conductors

Selection table for CWT range

CWT Specifications
Type Sensitivity
(mV/A)
Peak current
(kA)
Peak di/dt
(kA/uS)
Noise max*1
mV pk-pk
Droop
typ.
(%/ ms)
LF (3dB)
bandwidth
typ. (Hz) fL
Peak di/dt
(kA/us)
HF (3dB) bandwidth
typ. (MHz) fH*2
Peak di/dt
(kA/us)
Peak di/dt
(kA/us)
High Sensitivity Ranges of CWT .... measuring currents from 300mA
CWT015 200.0 0.03 0.2 6.5 130 150 2.0@6kHz 6 4
CWT03 100.0 0.06 0.4 4.5 90 105 2.0@4kHz 10 6.5
CWT06 50 0.12 0.8 3.0 70 80 2.0@3kHz 16 10
CWT1 20.0 0.3 2.0 2.5 40 50 1.9@2kHz 16 10
CWT1N 20.0 0.3 2.0 2.0 20 25 1.9@1kHz 10 5
CWT3 10.0 0.6 4.0 8.0 3.0 3.5 1.0@300Hz 16 10
High Sensitivity Ranges of CWT .... measuring currents from 300mA
CWT3N 10 0.6 4.0 14.0 0.9 1.0 1.7 10 5
CWT6 5.0 1.2 8 14.0 0.9 1.0 1.7 16 10
CWT15 2.0 3.0 20.0 7.0 0.7 0.8 1.3 16 10
CWT30 1.0 6.0 40.0 5.0 0.5 0.6 0.9 16 10
CWT60 0.5 12.0 40.0 5.0 0.5 0.6 0.9 16 10
CWT150 0.2 30.0 40.0 3.0 0.2 0.2 0.3 16 10
CWT300 0.1 60.0 40.0 3.0 0.1 0.1 0.2 16 10
CWT600 0.05 120.0 40.0 3.0 0.06 0.05 0.1 16 10
CWT1500 0.02 300.0 40.0 3.0 0.035 0.03 0.06 16 10
CWT3000 0.01 600.0 40.0 3.0 0.035 0.03 0.06 16 10
CWT6000x 0.005 1200.0 40.0 3.0 0.035 0.03 0.06 16 10

*1Distributed around the fL (3dB) bandwidth. Additional 50/60Hz noise of approximately 2mVpk-pk applies with AC 115V and 230V supplied CWT

*2The high frequency bandwidth is in part dependent on coil length. The values given are for a 700mm coil, a 300 –or- 500mm coil will have a higher fH

TYPICAL ACCURACY
(full scale)
Calibrated & traceable to UKAS ±0.2% with conductor central in the loop
Variation with conductor position in the coil loop typically ±1%
TYPICAL LINEARITY
±0.05% (full scale)
ABSOLUTE MAXIMUM VALUES OF di / dt (kA/µs)
(value must not be exceeded)
CWT 015, 03, 06
PEAK 40.0
RMS 0.9 @ 70℃
CWT 1N / 3N
PEAK 20.0
RMS 1.0 @ 70℃
all other CWT's
PEAK 40.0
RMS 1.5 @ 70 ℃ (further information available on request)
Coil and cable
COIL CIRCUMFERENCE ‘A’ (mm)
300, 500, 700 or 1000mm
COIL CROSS SECTION ‘B’ (mm)
(dependent on "Peak coil voltage isolation" see below)
8.5 (supplied with 10kV insulation as standard)
14.0 (with protection sleeve)
PEAK COIL VOLTAGE ISOLATION (kV)
10

Safe peak working voltage to earth. The coils are flash tested at 15kVrms for 60 seconds. The coil is supplied with a removable silicone sleeve which provides additional mechanical protection.

TEMPERATURE RANGE (℃)
-20°C to 100°C

For de-rating due to temperature cycling please consult Powertek

CABLE LENGTH (metre) (from box to coil)
2.5 or 4
powertekuk
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
A Universal Power adapter is included with the CWT probe (accepts 115Vac or 230Vac)
Rechargeable batteries and internal charger, option R, is available. (batteries are charged whenever external +12-24V dc supply is present). Typical recharge time 40 hrs, typical life 8 hrs.
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 drive capability optional.
TEMPERATURE RANGE (℃)
0℃ to +40℃
Ordering
Model
CWT unit is supplied with bnc-bnc cable, 12-24Vdc input, 4 AA batteries, power adapter and user manual, calibration certificate and carry case.
Cable length (m)
Coil circumference (mm)
e.g. order code = 6kApk, 4 AA Batteries, 12-24Vdc input, ac adapter, 2.5 metre cable, 500mm coil (Coil insulation is 10kV as standard)
CWT30B
2.5
500
e.g. order code = 6kApk, 4 AA Batteries, 12-24Vdc input, 230V ac adapter, 4 metre cable, 300mm coil
CWT30B
4
300
e.g. order code = 1.2kApk, 4 AA rechargeable batteries, internal battery charger, 12-24Vdc input, ac adapter, 2.5 metre cable, 500mm coil
CWT6R
2.5
500

All CWT clamp on current probes are supplied with bnc-bnc cable, 12-24Vdc input, 4 AA batteries, power adapter and user manual, calibration certificate and carry case. If you have any queries regarding the CWT or require specifications outside our standard ranges please do not hesitate to contact us.