CWT LF Wideband Clip-on type Current Probes, Current Sensor

Current sensing from low frequency 0.001Hz to 6.5MHz

The CWT LF current sensors are rugged clip on, flexible sense coil, high frequency current probes, using Rogowski Coil technology for wide bandwidth measurement and faithful conversion of ac 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.

Bandwidth 0.01Hz to 10 MHz (see bandwidth spec for each model)
CWT LF models available with extended LF bandwidth <1Hz
0.1 to 0.2 degree phase shift<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

CWT LF (low freq) datasheet CWT application notes CWT Calibration

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

Clip On Current Probes Specifications

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	Phase lead at 50Hz typ. (deg)	HF (3dB) bandwidth typ. (MHz) fH ^*2
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	Phase lead at 50Hz typ. (deg)	Coil Length 300mm	Coil Length 700mm
Standard Coils
CWT03LF	100.0	0.06	0.4	15.0	4.6	5.1	8.3	6.5	3.0
CWT06LF	50.0	0.12	0.8	15.0	2.3	2.6	4.2	6.5	3.0
CWT1LF	20.0	0.3	2.0	15.0	1.0	1.0	1.8	6.5	3.0
CWT3LF	10.0	0.6	4.0	15.0	0.5	0.55	0.85	6.5	3.0
CWT6LF	5.0	1.2	8.0	15.0	0.25	0.27	0.45	6.5	3.0
CWT15LF	2.0	3.0	11.0	15.0	0.1	0.11	0.18	6.5	3.0
CWT30LF	1.0	6.0	11.0	15.0	0.05	0.055	0.09	6.5	3.0
CWT60LF	0.5	12.0	11.0	15.0	0.025	0.022	0.045	6.5	3.0
CWT150LF	0.2	30.0	11.0	15.0	0.01	0.011	0.018	6.5	3.0
CWT300LF	0.1	60.0	11.0	10.0	0.007	0.008	0.012	6.5	3.0
CWT600LF	0.05	120.0	11.0	5.0	0.007	0.008	0.012	6.5	3.0
CWT1500LF	0.02	300.0	11.0	4.0	0.007	0.008	0.012	10.0	5.0
Miniature Coils 3.5mm dia and 4.5mm dia								Coil Length 100mm	Coil Length 200mm
CWT03LF	100.0	0.06	0.4	16.0	10.2	11.0	18.6	5.0	4.0
CWT06LF	50.0	0.12	0.8	16.0	5.1	5.6	9.3	12.0	7.5
CWT1LF	20.0	0.3	2.0	15.0	2.2	2.3	4.0	12.0	7.5
CWT3LF	10.0	0.6	4.0	15.0	1.0	1.1	1.7	12.0	7.5
CWT6LF	5.0	1.2	8.0	15.0	0.5	0.55	0.85	12.0	7.5
CWT15LF	2.0	3.0	14.0	15.0	0.2	0.22	0.35	12.0	7.5
CWT30LF	1.0	6.0	14.0	15.0	0.1	0.11	0.18	12.0	7.5
CWT60LF	0.5	12.0	14.0	15.0	0.05	0.055	0.09	12.0	7.5
CWT150LF	0.2	30.0	14.0	15.0	0.02	0.022	0.035	12.0	7.5
CWT300LF	0.1	60.0	14.0	15.0	0.01	0.011	0.018	12.0	7.5
CWT600LF	0.05	120.0	14.0	10.0	0.007	0.008	0.012	12.0	7.5

^*1Distributed around the fL (3dB) bandwidth
^*2For 2.5m cable length. Contact Powertek for values of fH for other coil and cable lengths

TYPICAL ACCURACY
(full scale)

Traceable calibration to ±0.2% with condcutor centrail in the lop Variation with conductor position in the coil loop typically ±1% for standard coils Variation with conductor in position in the coil loop typically ±2% for miniature coils

TYPICAL LINEARITY

±0.05% (full scale)

ABSOLUTE MAXIMUM VALUES OF di / dt (kA/µs) (value must not be exceeded)

(Standard Coil)

(Miniature Coil)

PEAK: 11.0

PEAK: 14.0

RMS: 0.8 @ 70°C

RMS: 0.85 @ 70°C

^*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)

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 (°C)

-20 to 100

For de-rating due to temperature cycling please consult Powertek

CABLE LENGTH (metre) (from box to coil)

2.5 or 4

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 (°C)

0°C 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)	CWT30LF B	2.5	500
e.g. order code = 6kApk, 4 AA Batteries, 12-24Vdc input, 230V ac adapter, 4 metre cable, 300mm coil	CWT30LF B	4	300
e.g. order code = 1.2kApk, 4 AA rechargeable batteries, internal battery charger, 12-24Vdc input, ac adapter, 2.5 metre cable, 700mm coil	CWT6LF R	2.5	700

All CWT LF 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.

CWT LF (low freq) datasheet CWT application notes CWT Calibration