In case of excessive use of the device, there is a chance that the accuracy will decrease over time. The instrument will readily drift apart in a humid, hot environment. While working with AC-DC variable power supply, one cannot take risks. Hence, you have to opt for electrical calibration to omit wrong calculations. Electrical calibration controls errors, quantifies issues, and minimizes uncertainties to an acceptable level.
Table of Contents
What is Electrical Calibration?
Calibration means comparing the measuring instruments to the standard devices. A standard should be ten times more accurate than the unit under test ( UUT) as a practice. Yet, the accuracy ratio of 3:1 is also acceptable. Calibration points out the need to repair the devices or change them accordingly.
Calibration is a broader concept to which electrical calibration is a branch. Whenever you undergo an adjustment process of digital multimeters, you need electrical calibration methods.
Electrical Calibration is the performance evaluation of instruments that tests electrical parameters. Current, Voltage, Resistance, Time, and Inductance are the principal parameters of these devices. Some other model parameters could be power factor and phase. While calibrating your device, you have two main objectives of
- Testing the accuracy of a piece of equipment,
- Inspecting the traceability of the measured value, i.e., whether it is reliable or not.
You will use a precision device for the performance characteristics of UUT. Remember, the precise device must have known certainty factors. There are two main types of precision devices.
- Calibrator and Standard
- Precision measurement devices like precise digital multimeters or ratio bridges.
Often calibration of your device minimizes the errors of the taken measurements.
Calibrator and Standards
With a calibrator, you measure a wide range of output signals. These precision output signals can vary from as little as a few microvolts to as much as kilovolt. Also, it provides signals for electrical functions as resistances, current, and voltage.
Since a standard could measure a value four times better than the calibrator. Thus standards are more specific devices. But the precision may cost them their multifunctionality. Hence, standards might only measure a single electrical function or limited output ranges.
Precision Digital Meters, Measurement Standards, or Ratio Bridges
Precision digital multimeters (DMMs) have excellent measurement performance on many electrical parameters. Functions include voltage, resistance, currents, and sometimes frequency and capacitance.
Besides DMMs, there are more precise measurement devices. You may know them as the measurement standards or ratio bridge. Ratio Bridges may offer less functionality. But accuracy is higher than the precision DMMs.
How to select a Calibrating Solution?
When dealing with a power source, you need tools to measure the current and voltage. So, whether you use oscilloscopes or multimeters, you have to repair them on time.
As the rule of thumb, the standard should be 4 times more accurate than the unit under test. Also, the selected calibration tool should be according to the type of testing device.
Keep in mind that the manufacturers have precautionary measures for every device. So you have to consider the manual before using the test as well as the calibration instrument. If not followed, the units will no longer be able to perform any function.
There is another term that you might be familiar with, known as compliance. It is the limited amount of electrical drive an electrical load may need. Each type of calibrator has its tolerance for the signal. If you supply sufficient drive, the output will not be compromised. Thus you have to be careful with the compliance signal.
Moreover, devices like panel meters are heavier in load. They may need a compliance drive signal more than other instruments. So when you are calibrating with such tools, you will need a robust electrical drive to activate them. Again, lesser or more drive than the device needs will result in forged output readings.
ISO 17025 Accreditation
For a laboratory, it is crucial to verify itself on ISO 17025 standard. The ISO standard assesses a test place for some factors. Hence the goal is to check the ability of the lab to test the precision and produce a calibration dataset. Major factors are:
- Comparison of calibration tools and measured data to predefined standards
- Inspection of technical competency of the team who performs calibration
- Equipment maintenance
- Calibration dataset and test’s quality check
- Validation of a testing method
- Appropriate transportation of test equipment
- Quality of test environment and sampling
Procedure for Electrical Calibration
Generally, you take the results from a device of unknown precision. Then you compare it to the standard or reference device. The uncertainty of the precise device is known. Also, it has to conform to the international standards of calibration. Following are the steps you will perform in a calibration process.
- First, assess the calibration capability of a device and switch it on. Let it stabilize for a few moments.
- Next, complete the initial verification and troubleshooting of the instrument.
- After that, set operational parameters and connections. Adjust the calibrator and control it.
- Now, take the measurements from both devices. Check the results and analyze the uncertainty factor.
- In the end, report the results and issue a calibration certification for the future.
How often to repeat the Electrical Calibration?
The cost of calibration and frequency is industry-specific. There are industries with higher risk factors involved in the line of work. Therefore, they have to perform the calibration test more frequently.
Most industries go for an annual calibration check as per the rules. With time, you get the calibration of multimeters and other electrical instruments done. Depending upon the results, you must adjust the test frequency or update the devices if you need.
As you consult professional calibration consultants, you will get a calibration certificate. This certification is proof that you have tested the tools with objective standards.
Also, it shows that the measuring device is now all set to produce stable readings with less error rate. Always remember that you have to perform the calibration on the testing device as well. It is necessary so that they remain fit for inspection.
Calibration is often done to maintain the quality of a calibration facility. For that, you will use a precision sourcing device or a precision measurement device, and a precision sourcing device tests the measurement instrument with similar performance specifications.
Similarly, a measurement instrument maintains the sourcing device. Thus, your lab should have each type of instrument. Systematic comparison will keep the tool providing consistent and accurate measures. Here at Cloom, we offer custom wiring assembly with attention to each detail. Thus you can perform your calibration tests with precision. To avail of our services, contact us now.