Electrical measurement tools are essential accessories used for the performance evaluation of an electrical circuit or for troubleshooting in case of any malfunction. Among measurement tools, the most common or basic tool is a digital multimeter or clamp meter. A clamp meter is quite similar to a multimeter in functionality but is preferable in certain scenarios. We’ll explain how to use the clamp meter and what its advantages are for taking certain measurements.
Getting Familiar With the Digital Clamp Meter
Before working with electrical or electronic systems, it is important to be familiar with safety protocols for using electrical gadgets or tools. These include understanding the operational limits of the device or tool and ensuring personal safety/insulation, where required.
When you unbox the digital clamp meter, you will see that it has hinged jaws and two wire test probes—commonly a red and a black probe. Plug the red probe into the meter’s positive jack terminal (often denoted by measurement symbols such as V, Ω, Hz, Duty Cycle, diode symbol) and the black probe into the common (COM) jack terminal. We use these probes to connect the measurement points on the device under test to the digital clamp meter.
On the clamp meter, you will also find buttons or dials to select the appropriate function for electrical measurement. On the clamp meter and its test probes, the operational category (like CAT I, CAT II, etc.) is usually mentioned in its OEM’s product description, along with its operational suitability and limits.
How a Digital Clamp Meter Measures Resistance
A digital clamp meter operates by providing a constant current source to the resistor (under test), and then measures the voltage across it. It then uses the current and the resulting voltage to calculate the resistance usingOhm’s law.
The process with a clamp meter is similar to that way in which wemeasure resistance using a digital multimeter. First, set the clamp meter to measure resistance by turning the selection knob to the Ω symbol. Take an axial resistor and place the (two) probes of the clamp meter across the two ends. The LCD screen on the digital clamp meter will display the measured resistance value. You can also verify this valueusing the resistor color-coding method.
It is important to note that the measured value of a resistor placed in a circuit may be different due to effective resistance resulting from series or parallel combinations. With a clamp meter, you can also measure the resistance value of any SMD resistor, any electrical path, or even wire using the same method as described for the axial resistor.
How a Digital Clamp Meter Measures Voltage
Almost all digital clamp meters have a voltage measurement function, generally used to measure and verify the outputs of devices, components, or circuits. Select the voltage measurement function (AC or DC) on the digital clamp meter.
Voltage measurement is always conducted between two points in an electrical assembly, which involves using two probes: place the red probe on the test point on the circuit or system for which the voltage measurement is required and the black probe for the reference level (typically ground). On the meter’s display, you’re able to observe the measured voltage. Swapping the probes on these points would simply invert the measured voltage.
There are two different modes for measuring voltage: direct current (DC) and alternating current (AC). DC can be precisely measured, while AC is usually measured as a root-mean-square (RMS) value. DC is represented by a V with one dashed line and one solid line while AC is represented by a V with a wave symbol. verify you select the correct range and mode for your application.
Working with high-voltage DC and AC is only advisable for those who are familiar or experienced with electrical safety protocols.
How a Digital Clamp Meter Measures Current
Measuring current with a digital clamp meter is relatively easy. A clamp meter can measure the current flowing through a conducting wire with or without insulation covering on wire. For accurate current measurements, the wire under test should be isolated from other wires. you may measure both DC and AC currents by selecting DC or AC mode using the SELECT button and choosing the appropriate current range (e.g., 40A or 400A) from the rotating dial or buttons.
Press the REL (Relative) button to set the meter reading to zero to establish the reference point for the current measurement. To measure the current, place the current-carrying wire or conductor between the digital clamp meter jaws, while the current is flowing through it. This allows you to measure the current without interrupting the circuit or causing any power loss or damage. Also, ensure that you place the conductor perpendicular and in the center of the jaws. This positioning allows the jaws to act as a coil around the conductor when closed.
Performing a Continuity Test Using a Clamp Meter
Electrical continuity means the presence of a complete path for current flow. We can use the digital clamp meter’s continuity test mode to test fuses, wires, electrical connections, conductors, and other components. It looks for the electrical continuity and minimum resistance between the two test points.
It is important to note that you should cut the power off during continuity testing. This is not primarily for safety; rather, continuity is tested by sending a minute electrical current through the two test probes and observing the resistance of this current. If there’s any other electrical current at the same time, the clamp meter won’t be able to read the correct resistance between the two probes.
To perform the continuity test, turn the selection knob to the diode symbol (►). In some digital clamp meter models, you may have to use buttons to enable this feature. If enabled, you will observe the V or Ω symbol on the clamp meter LCD. Place the test probes on the points where you want to check for continuity. Test probe polarity in this case usually does not matter. A clamp meter gives an audible response (a beep) in Ω selection when it detects a complete path with the tiniest resistance (typically < 10Ω) and no beep when the path is either open or has significant resistance (typically > 31Ω).
This audible response allows the user to focus on testing procedures without looking at the clamp meter display. With the test probes separated, the digital clamp meter’s display may show OL (overload).
Performance Comparison
Digital clamp meters and digital multimeters both measure basic electrical parameters in a similar way but differ in how current measurement is performed. A clamp meter can measure current without interrupting the circuit, making this tool ideal for taking measurements in tight spaces or testing live wires, making it relatively safe to operate as well. A clamp meter is typically used to measure relatively high-level currents. However, it is generally less sensitive to very small currents.
A digital multimeter requires the electrical probes to be placed in current-measuring configuration, i.e. probes be placed on the terminals in series between which the current is required to be measured. Note, however, thatdigital multimeters can measure currentmore accurately than clamp meters.
Electrical Measurement Using a Clamp Meter Is Easy
A clamp meter is a must-have tool for electrical professionals, enthusiasts, and hobbyists. It gives essential diagnostic and analysis parameters to work with the electrical or electronic systems without physically disturbing the electrical wiring. With simple probe placement, you can ensure connectivity and measure various parameters.
For current measurement, just select the measurement option and enclose the current-carrying wire within the hinged jaws to get the current value. Proficiency in these measurement skills makes the job quite easy for a professional or hobbyist.
