Introduction
The CA10 Current Sensor Adapter is programmable and customizable to work with third-party current measurement devices that output voltage or current signals proportional to measured current. After programming and configuring the CA10 for a given current transducer/transformer, a compatible Teledyne LeCroy oscilloscope or Motor Drive Analyzer recognizes the device as though it were a native Teledyne LeCroy current sensor. Examples of devices that can be used with the CA10 include Pearson current transformers, Danisense current transducers, PEM-UK Rogowski Coils, or any conventional turns-ratio current transformer. This technical brief will walk through the setup and use of a PEM-UK Rogowski Coil with the CA10, which outputs a voltage relative to the sensed current flow.
PEM Rogowski Coil
PEM is a manufacturer that focuses on products using Rogowski technology. Look up their product information at: http://www.pemuk.com/.
The model used in this example is the LFR 1/15, as shown in Figure 1. The LFR 1/15 has a peak current rating of 3.0kA and outputs a voltage proportional to the measured current. It can either be powered by a single 9V PP3 battery or by an external power supply.
Setting up the CA10
Upon connecting the CA10 to a Teledyne LeCroy oscilloscope or Motor Drive Analyzer, a prompt will ask if you want to program the device. Selecting Yes opens the CA10 dialog (Figure 2).
The current sensor information, scale factors, and channel definition settings can all be defined in the CA10 dialog. The setup for the LFR 1/15 PEM Rogowski Coil is as follows:
- Model: LFR 1/15
- This field changes the name of the CA10 setup dialog tab to the model of the third party sensor (Figure 3).
- Serial Number: 19541-0515
- The serial number is specific to the particular sensor being used. It can usually be found on the sensor device.
- Vertical Unit: A
- The vertical unit will always be Amps with the CA10
- Units/V(slope): 50
- This is the Amps/Volt setting, which is the multiplication factor by which the input will be scaled. This setting is specified by the manufacturer of the current sensor for devices that output a voltage, or is based on the transformer ratio and shunt resistor used on a current transformer.
- Y-Intercept: 0
- This number is added to the rescaled Amps/Volt result. In many cases, this value is zero unless a specific offset number is required.
- BW Limit: Full
- Choices include Full, 200 MHz, or 20 MHz. This applies a filter at the bandwidth specified to the input signal.
- Input Termination: 1 Mohm
- Choices include 1 Mohm or 50 Ohm. The current sensor’s manufacturer specifies the required termination.
- Input Coupling: Both
- Choices include AC, DC, or Both. Choosing either AC or DC forces the CA10 to always couple to that particular setting. With Both chosen, the user can choose either AC or DC in the Channel dialog each time the device is used.
After entering all the settings, press the Save to Adapter button to program the adapter. The CA10 is now programmed to be recognized as the PEM Rogowski Coil. With subsequent usage on any channel on any compatible Teledyne LeCroy instrument, waveforms will automatically be correctly scaled in Amps. The CA10 is provided with heat-shrink tubing to apply to the BNC cable connection so that the current sensor can be semi-permanently attached to the CA10. This helps ensure correct and consistent results using the current sensor, eliminating the possibility of human error that can arise from manual rescaling. Figure 4 shows the CA10 connected to the LFR 1/15 PEM Rogowski Coil with application of the clear heat-shrink tubing provided with the CA10.
Conclusion
The CA10 Current Adapter provides an alternative to expensive current probes. This relatively low-cost adapter can be used with a wide variety of third party current-sensing devices. The ability to program the current sensor information directly to the CA10 allows seamless use of the third-party sensor without the need to manually rescale the waveforms with each subsequent use.
