A digital clamp meter is one of the most common electrical measurement tools available, due to its ability to measure current through non-contact means. It’s helpful in an array of situations, such as power maintenance, electrical testing, and general troubleshooting. However, like all measurement tools, clamp meters will eventually experience drift and start producing inaccurate, unreliable results.
In this article, we’ll discuss the importance of calibrating clamp meters, provide an overview of how to calibrate clamp meters and which calibration tools are essential to calibrating clamp meters.
Why Calibrate Your Digital Clamp Meter?
A digital clamp meter, like any measurement tool, undergoes natural wear and tear with regular use; it needs routine maintenance to continue performing at peak precision. Calibration provides critical insights and corrections to ensure clamp meters continue to produce the reliable, precise readings that are necessary to verify, troubleshoot, and solve issues in electrical systems. In short, taking the time to calibrate clamp meters saves time, money and prevents potentially dangerous electrical conditions.
What Tools and Equipment Are Used To Calibrate a Digital Clamp Meter?
The base list of equipment for digital clamp meter calibration is fairly simple. You’ll need a clamp meter, multifunction calibrator, and a current coil. (If your current is greater than 1,000 amperes (amps), you’ll need to pair the coil with an amplifier.)
Clamp Meter
Depending on the typical use case of whoever will actually be using the clamp meter, there could be different types of clamp meters you’ll be calibrating. Usually, they’ll fall into one of these three categories:
Some popular clamp meters on the market include:
- Fluke 376 FC True-RMS Clamp Meter
- Fluke 381 Remote Display True RMS AC/DC Clamp Meter
- Fluke 325 True RMS Clamp Meter
Multifunction Calibrator
A good calibrator should have broad workload coverage and enough compliance voltage to complete the calibration accurately. Fluke calibrators use “L-COMP,” or inductive compensation, to increase the available compliance voltage. The calibrator must also be compatible with current coils, otherwise, you’ll run into issues.
Some popular multifunction calibrators on the market include:
- 5080A High Compliance Multi-Product Calibrator
- 5560A, 5550A, 5540A, and 5530A Multi-Product Calibrators
Current Coil
The coil you use while calibrating a clamp meter has to have enough turns to accurately test the entire range of the clamp meter. More turns allow for lower source amperage and more efficient and safe calibration.
Some popular current coils on the market include the Fluke 50-Turn 5500A/Coil.
Current Coil Amplifier
If you need to measure current that exceeds 1,000 amps, you’ll need a current coil that includes an amplifier.
Some popular amplifiers on the market include:
How Do You Calibrate a Digital Clamp Meter?
Calibrating a digital clamp meter can seem daunting, but with the correct knowledge and tools, it’s fairly straightforward.
- Evaluate your clamp meter: Check that nothing is wrong with the clamp meter itself. Make sure it’s clean and hasn’t suffered any damage that might alter the readings. Check the state of the batteries and exchange them for new ones if necessary.
- Check the manufacturer’s specifications: Use the specs to confirm that you have the necessary equipment and know the tests you need to perform on your clamp meter in order to calibrate it.
- Connect to the calibrator: Using a multifunction calibrator, such as the Fluke 5560A, connect a coil into the proper output terminal.
- Clamp the coil: Clamp the clamp meter onto the coil, such as the Fluke 5500A/COIL. Begin outputting the desired current and note the value on the clamp meter. Check the specifications to see if the readings are within acceptable manufacturer tolerance.
- Adjust the clamp according to manufacturer’s instructions: If any readings don’t match the range(s) indicated in the specifications, then it’s time to properly calibrate your clamp meter.
Best Practices for Digital Clamp Meter Calibration
Once you’ve got the right tools for the job, here are some tips for the optimal clamp meter calibration experience to keep in mind.
1. Not All Clamp Meters Are the Same
Remember that there are different types of digital clamp meters that can have physical features that differ from each other. The size, shape, and function of a clamp meter will vary depending on the model and its intended use case. Given these differences, there may be variations in the calibration process, too. For instance, the jaw width on one clamp meter might be not be compatible with certain coils, so you’ll need to ensure your calibration system has the right components.
2. Strive for Repeatable Measurements
If you’re unable to consistently and reliably replicate measurement results during calibration, something is wrong. Focus on the placement of the meter itself to keep the measurements easily repeatable, particularly the alignment of your clamp on the coil. Misalignment of the jaws can produce an error or otherwise cause issues with the measurements.
3. Watch Out for Hot Coils
Current running through coils generates heat. Make sure to avoid contact with coils during calibration and shortly after it concludes. In order to ensure a safe calibration process and prevent overheating, know the maximum operating times of any coils you might use during high-current calibration.
4. Inspect Coils Regularly
The heat that coils generate during clamp meter calibration can often lead to bending of or damage to the coil itself — both of which can cause measurement errors. Check coils regularly to confirm they’re still in sound physical shape and operating properly.
5. Be Aware of Voltage Limits
Stay within the parameters of the machines and accessories you’re using in order to guarantee a safe and accurate calibration process. Different calibrators will have different capabilities with different coils, so check documentation to verify you have the equipment that can handle whatever voltage levels you need to test.
6. Calibrate Meter Accessories, Too
Don’t forget to calibrate all parts of the clamp meter system. Even if you’ve calibrated the clamp meter itself, it’s a moot point if you don’t also calibrate the accessories that end users frequently use with the clamp meter, like probes.
Create the Best Clamp Meter Calibration System
Want to learn more about the best tips and tools for calibrating your clamp meters? Check out Fluke’s selection of electrical calibration equipment and read these other resources: