What is a current clamp and how to choose the most appropriate
A measurement clamp (current clamp, wattmeter clamp, etc.) is a multimeter that incorporates a pincer-shaped current sensor, inside of which the electrician places the conductive wire over which the measurements are to be taken.
In this article:
What are the benefits of using a wattmeter clamp?
The wattmeter clamps and thus any measuring clamps have a number of advantages over the classic multimeters such as:
- They do not break down when measuring high current values. Unlike a multimeter, which tolerates currents of a few amperes for a limited time before their circuitry gets damaged, the measuring clamp can continuously measure values as high as several kA and can even be used for continuous monitoring tasks and for datalogging purposes.
- Greater security. The current measurement is taken by induction (it is a contactless measurement), so that it is not necessary at any time to work with the exposed parts of a conductor or of an electrical circuit.
- Efficiency. It is not necessary to turn off the electricity supply to take the measurements, therefore not only the electrician will save time but also the subscribers will not suffer from the inconvenience of a power cut.
Using a CT-317 wattmeter clamp
Do an electrician really need a measurement clamp?
Until recently, an electrician could manage without using of a current clamp or a wattmeter clamp. However, nowadays more and more solar energy panels are being installed and also more electric vehicle chargers, so the demand for energy and current measurement has evolved. And it has done so to a point that it goes beyond the measuring capabilities of the digital multimeters.
Therefore measurement clamps are becoming a must for the electricians becoming one of the essential instruments in their toolkits, no matter their scope.
How to choose a measurement clamp
There are two main variables to consider that are closely related: The maximum current supported by the clamp and the expected application or scenario.
- Choosing a clamp by the maximum current allowed: As a general rule, the larger the inner diameter of the pliers, the greater the current that can be measured by the clamp and therefore the instrument can be used in domestic, industrial, photovoltaic, etc. applications.
- Choosing a clamp by the application. The needs of an electrician are different depending on whether the field of application comprises domestic or industrial installations, single-phase or three-phase, etc.
- For the measurement of domestic installations in homes or premises: A basic current clamp meter perfectly covers the requirements.
- For the measurement of industrial installations: It is necessary to make use of current clamp meters that can work with voltages of up to 1000 V and currents close to 1 kA.
- To deal with photovoltaic energy: A current clamp meter with high DC measurement capacities.
- Measurement of the electrical supply quality: The market offers wattmeter clamps for balanced or unbalanced three-phase electricity supply, whatever is necessary.
Current clamps for photovoltaic energy (PV) installers
As a rule, measurement clamps are designed to work in alternating current (AC) scenarios. Photovoltaic current clamp meters can measure higher voltages and currents in direct current (DC) than a regular measurement clamp.
- CT-317. Current clamp meters for self-supply domestic PV installations. It can reach values of up to 1000 V in direct current (DC).
- IC-620. Clamps for industrial PV installations with extended measurement capabilities up to 1500 V and greater safety requirements.
It is essential to use a wattmeter clamp to measure the actual power consumption and the quality of the supply of a domestic or an industrial installation.
- CT-327.Wattmeter clamp for balanced three-phase systems (with a separation of 120º between phases) and also for single-phase. This model includes the measurement of harmonics, which is basic to evaluate the quality of the electricity supply in those scenarios where a large disturbance of the waveform is expected due to the massive presence of machinery, variable speed drives, ballasts, power supplies, etc.
- IC-640.Wattmeter clamp for unbalanced three-phase systems.
They are the most common instrument used by electricians both in domestic and industrial environments. What makes these measuring clamps interesting is their ability to supersede a multimeter because in addition to measuring voltage and current, they have all the measurement capabilities of a tester.
- CT-337. Smart current clamp meter with automatic selection of measurement type and margin.
- CT-347. CT-347. an evolution of the CT-337 which also includes a temperature probe. It is perfect to evaluate the overheating in the facilities.
Leakage current clamps
To locate the small leakage currents that can trip the protective devices in an electrical circuit, it is required a clamp with a high sensitivity capable of measuring very low currents. The model CT-237 is suitable for domestic and industrial installations because it can work in both low frequency and high frequency systems.
- CT-237. A clamp meter specially designed to measure leakage current in low frequency and high frequency systems.
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