Leakage current clamps are valuable diagnostic instruments for the electrical and electronics professional. In contrast to conventional current clamps, a highly sensitive leakage current clamp can also detect and reliably measure very small currents. This enables, for example, the measurement of leakage and differential currents in electrical systems according to DIN VDE 0100 / 0105 and on devices according to DIN VDE 0701-0702 and machines according to DIN VDE 0113-1, DGUV regulation 3. The CM 9-1 is therefore also an ideal supplement to safety test devices.
This practice-oriented application report shows examples of possible applications of modern leakage current clamps and provides electrical specialists and service technicians with helpful tips for daily use.
The function of the leakage current clamp Just like the current clamps normally used, a leakage current clamp also functions by means of indirect measurement.
This means that, in contrast to direct measurement, the circuit does not have to be disconnected and therefore there is no interruption in the operation of the system. The measuring point to be checked only has to be covered with the hinged measuring clamp (the current transformer) and then induces a current in it which is evaluated in the highly sensitive measuring transformer of the BENNING CM 9-1 and shown on the display.
Special features and advantages of the leakage current clamp
The extended application possibilities of the BENNING CM 9-1 lie in the detection of very low currents down to 1 µA AC. This allows, for example, the detection of insulation faults without having to switch off the system to be tested. A great advantage of leakage current measurement is that differential currents can also be measured. In contrast to direct measurement via the PE conductor, the measurement result is displayed correctly here even for test specimens and systems that are not installed in isolation.
Differential currents occur when the sum of the currents flowing into the system is not exactly equal to the sum of the return current. This is due to defects in the insulation, but also to mains filters. The result is leakage or leakage currents which flow either via the protective conductor (PE) or via electrically conductive plant components.
The BENNING CM 9-1 with True-RMS measuring method precisely records these unwanted currents and allows easy monitoring of the permissible limit values.
Fields of application and applications
Repeat tests and tests after repair of mobile consumers in accordance with DIN VDE 0701-0702
Three-phase loads can be tested quickly and reliably using the BENNING measuring adapters 044127 and 044128.
The leakage current clamp BENNING CM 9-1 measures either the differential current over all active conductors (L1, L2, L3 + N) or the leakage current over the protective conductor (PE).
The read measured values can be entered directly on the BENNING ST 750 A device tester, which simplifies testing considerably. A suitable test sequence is already stored in the device tester.
Leakage current measurements on systems that cannot be switched off
In IT and industrial environments, devices and equipment for troubleshooting and inspection often cannot be switched off without further ado.
With the leakage current clamp BENNING CM 9-1 it is possible to precisely detect residual currents without disconnecting the circuits and also to carry out current measurements in the system.
Troubleshooting is greatly accelerated and expensive downtimes are avoided.
Finding and isolating hum currents
Unwanted compensation currents can lead to considerable problems. The function and accuracy of measurement and control circuits are impaired, and audio and video signals are disturbed.
These undesired currents cannot normally be reproduced with conventional, direct measurements. With the BENNING CM 9-1, on the other hand, the service technician is able to quickly identify such problems and eliminate the fault.
Load current measurements in an industrial environment
Increasingly, consumers and controls are being used which draw or emit non-sinusoidal currents.
These include, for example, frequency converters for electric motors, clocked power supplies and many power electronics.
Conventional (RMS) current clamps inevitably measure such currents incorrectly, while the BENNING CM 9-1 also displays correct values here using the True-RMS measuring method.
Versatile application possibilities
For service technicians, the BENNING CM 9-1 provides many other useful applications in daily practice. For example, factory customer services use the CM 9-1 – in addition to safety tests – also as an ideal diagnostic instrument.
The measured current consumption of the device makes it very easy to monitor functional sequences, such as the activation of a heating element, and classify them as “o.k.” or “not o.k.” without having to carry out time-consuming disassembly work in order to reach the corresponding measuring points inside the device.
The fully automatic background lighting of the BENNING CM 9-1 allows convenient reading of the clear, 4-digit display at any time, even in poorly lit environments, for example when measuring in control cabinets. The clearly readable LCD also integrates a fast-reacting bargraph display.
The selected measuring range, alarms and special functions are shown simultaneously in the display for optimum clarity and ease of operation.
Handy, robust and precise
Generous 23 mm for pliers opening and pliers diameter make it possible with the BENNING CM 9-1 to easily cover even thicker cables or strong cable bundles.
This, together with the maximum measuring current of 60 A, also allows the use for conventional measurements, which would otherwise require an additional current clamp.
In interference-loaded environments, a complex shielding of the measuring clamp against foreign fields ensures maximum precision and immunity to interference. A switchable low-pass filter can also be used to suppress higher-frequency interference, which is particularly advantageous in industrial environments.
Accessories and advantages
The BENNING CM 9-1 is delivered ready for use with the necessary measuring cables, batteries and a transport and protective bag.
The scope of delivery also includes a detailed, multilingual operating manual with numerous illustrated and easy-to-understand application examples.
The detailed operating instructions and the intuitive operation of the BENNING CM 9-1 also enable users who have not previously worked with a leakage current clamp to use it immediately and productively without a long training period.
The low purchase price compared to products from other brand manufacturers, the well-known high quality of BENNING and many helpful additional functions make the BENNING CM 9-1 an indispensable tool for every electrician, electronics engineer and service technician after a short time.
In addition to the BENNING CM 9-1 TRUE RMS leakage current clamp described above, you will also find the version with Bluetooth® function and app in the reichelt online shop: BENNING CM 9-2
Images: BENNING
