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Series L In-Line Non inductive co-axial current shunt

Current viewing resistor (CVR) Series L



Small terminating type CVR available with BNC, GR, UHF, N, HN and C connectors
Other connector options available upon request
Standard connections are the "S" input (8-32 stud with threaded case) BNC output connector
Series L Inline Drawing pdf

  • 0.01A to 5Arms continuous
  • 140A pulse for 1mS (depending on model)
  • DC-200 MHz frequency range
  • Extends current range of Scopes, DMMs and Wattmeters
  • Use with phase angle meters
  • BNC, GR, UHF, N, HN and C connectors
  • Insulated enclosure optional
  • Traceable to international standards via NIST (USA) and UKAS (UK)
  • Lifetime warranty

Inline Co-axial CVR's are particulary useful in circuits where insertion of the CVR between current source and load is necessary.  They are designed to minimize impedance mismatch when utilized in the 50-ohm systems.  Either end of the inline CVR may be used as the input.  However, as shown in the schematic, reversal of the designated input and output will produce a polarity reversal of the monitored signal.  Note that in the orientation shown the CVR output signl is in phase with the input current.  Performance of the inline CVR is independent of its location in the source to the load cable.  If, however, the CVR is not used at the load, two precautions must be observed.  First, the transit time of the connecting cable will produce a delay between the CVR output and the current at the load.  This delay is normally about 1.5 nsec. per foot of cable.  Second, if voltage across the load is also monitored, inductance will in general produce a potential difference between the voltage divider and the CVR grounds.  The resulting current flow in the outer conductors of the oscilloscope signal cables may produce waveform distortions.  This distortion is seldom evident in the current waveform, but oscillations in the voltage waveform are probable.

Non inductive Co-Axial Current shunt - CVR applications

  • Pulsed current applications for example GaN
  • Switching current applications GaN
  • Calibration laboratories for HF current
  • Current sensing for phase meters
  • High Frequency Watt Meters and Power analyzers
  • Current transformer calibration
  • Current probe phase delay characterization
  • SCR current measurements
  • Current control of automatic welders
  • Measure output of automotive alternators
  • Fault current detection to determine spark erosion bearing wear of ac generators
  • Electron beam welding
  • Current detection in detonation systems
  • Three-phase fault testing in power transmission substations
  • Fault detection in modulators
  • Measurement of laser system lamp currents
  • IGBT chopper current control in electric cars
  • Circuit breaker testing

About the Series L current viewing resistor (CVR) / non-inductive co-axial shunt resistors

The Series L range are High Frequency non inductive shunts designed to operate, with both AC and DC power systems, especially where phase angle and propagation delay is a consideration (GaN applications), Very useful for adding or extending the current range of Power Analyzers, Phase Angle Meters, Frequency Response Analyzers.  Using the Series L with phase angle meters allows phase angle measurement between voltage-voltage, voltage-current or current-current, ideal for phase protection relays, energy meters and current transformer calibration.

CVR's are rugged high frequency resistors designed to sustain very high peak power and current inputs generated by capacitor banks, pulse generator systems and steady state current loads. Their linear response over a broad frequency band provides an accurate indication of current magnitude free from inductive components. Inherent in CVR design is a coupling between the major electrical parameters of resistance, bandpass, energy capacity and wattage rating. This means we provide a wide ranging series of standard units covering a broad range of specifications.


Although most CVR's are designed primarily for pulsed or surge current measurements, their rugged construction and their low temperature coefficient resistive elements have made them ideally suited to a number of steady state applications. An average wattage rating applicable to continuous current loading is thus quoted for each resistor series. Care should be taken in circuitry involving either AC or high duty cycle pulse currents that this rating not be exceeded, since CVR damage by overheating can result. If requested we can supply resistors with special construction which will increase the standard wattage rating to a high value depending on the model.


Bandpass of a CVR is essentially flat from DC to an upper limit determined primarily by skin effect in the resistive element. Associated bandpass is based on a measured 10% to 90% risetime response to a step function of current produced by a coaxial line pulse generator. The di/dt of the test pulse exceeded 10^12 amps/sec.


Unless otherwise specified, resistors are supplied with resistance tolerance of ±4% of nominal value. In addition, a Kelvin Bridge determination of its exact resistance, accurate to ±0.2% is supplied with each unit. A wide range of special resistance values for any of our standard units can be supplied.


Case construction of all coaxial CVRs is silverplated brass. Standard output signal connector is BNC with other connectors available. Large coaxial CVRs utilize a high current flange and coaxial threaded stud input connections. Powertek's flat configuration CVRs, the Series W, originally developed for flat plate transmission line installation, are available in a wide range of unit widths and input configurations and have been found to be particularly useful in applications requiring resistors with extreme energy and wattage ratings.

World-wide Traceability

All measurements made using the CVR Series L shunts are traceable to National and International standards; through the measurement standards of Powertek. All CVR series L shunts are supplied with a certificate of conformance necessary for quality assurance standards such as IEC17025/ISO9001. Independent measurement certification is possible using UKAS, A2LA or Z540/NAVLAP certificate.




Small terminating type CVR available with BNC, GR, UHF, N, HN and C connectors
Other connector options available upon request
Standard connections are the "S" input (8-32 stud with threaded case) BNC output connector
Series L Inline Drawing pdf


When ordering specific series, input and output connections, model and signal output connector
Example: LR31MF-1-05-BNC; Series L; R31MF - Input and output connectors (Reynold 31 male & female); 1-05-Model (Series A, A-1-05); BNC - Output signal connector