The intricacies of electrical calibration make it a complicated process to understand that’s difficult to do yourself. Properly calibrating electronics requires more than just twisting a few knobs. Engineers who do this job must know about regulatory standards and how to meet them, the basics of the equipment, specifics of the instrument’s brand and much more.
What Is Calibration?
The only way to know whether your instruments give accurate readings is through regular calibrations. These services ensure that your devices measure according to standards set forth by national and international groups, such as the National Institute of Standards and Technology (NIST). Any electronic device that takes measurements and gives readings needs regular calibration to ensure it works correctly.
With electronic calibration, the engineer inputs a known value into the device and sees how far off the equipment’s reading is from the amount. The closer the output is to the known input, the better calibrated the equipment is.
With calibration, you may hear about the accuracy ratio and uncertainty. Accuracy ratios are older measurements that some use to understand how the instrument compares to a standard. This ratio refers to the value of the measure to the instrument’s accuracy, and most engineers aim for a 4:1 ratio. Using this value lowers the chances that the standard will impact the accuracy of the instrument’s calibration.
Mathematically, the test accuracy ratio (TAR) is equal to:
- TAR = (tolerance of unit under testing) ÷ (tolerance of standard)
One way of thinking about this measurement is the standard or testing equipment tolerance must be four times more accurate than the tolerance unit under testing (UUT). For example, if the standard requires a tolerance within 0.1 measurement units, and your device has a tolerance of 0.4 units, then the instrument has a 4:1 accuracy ratio. Since testing equipment and your operation’s electronics have both improved technologically, rates of 4:1 are challenging to achieve without adjusting the calibration tolerance of the device being tested.
Uncertainty is a better way to address the possible range of measurements that an instrument returns. It comes from the discrepancies of returned values reasonable based on the amount measured. This factor is so critical that all laboratories with ISO 17025 certification must include uncertainty analysis in their reports. Engineers may use uncertainty analysis when the TAR is less than 4:1.
The standard uncertainty is essential when calculating the tolerance uncertainty ratio (TUR). This measure divides the tolerance of the UUT by the standard’s uncertainty.
- TUR = (tolerance of UUT) ÷ (uncertainty of standard)
The above information will help you to better understand the report you get from the engineer who calibrated your equipment.
The Purpose of Calibration
You must calibrate your equipment if there is a chance that it may produce an incorrect output. How often you need to do this depends on several factors, including the following:
- The age of the equipment
- Recommendations from the last calibration certificate
- Changes in the environment
- Transporting the equipment
- Manufacturer’s recommendations
- Maintenance and service history
- The tendency of the device to wear and produce inaccurate results from use or storage
- Frequency and severity of use
These elements will help you to determine how often you must calibrate your equipment. If you have calibration done too infrequently, you could inadvertently use equipment that returns measurements outside the acceptable range of uncertainty. Regular calibrating ensures that your equipment operates as intended and without error.
When you regularly schedule a technician to calibrate your instruments, you can have more confidence in the output of your equipment. In specific industries — aerospace, pharmaceuticals, medicine and defense — the accuracy of the electronics used could save lives. Since lives depend heavily on the readings from your electronics, you need to be certain that it provides accurate information. To do this, you must have professional, certified calibrators handle your equipment.
In addition to saving lives, calibrating instruments has multiple other benefits, such as:
- Correcting manufacturing tolerances
- Allowing for the use of lower-cost components with higher manufacturing tolerances
- Reducing end-user customer concerns
- Improving the reliability of equipment
- Lowering warranty costs
- Decreasing test time
- Improving product delivery times
These benefits come with proper calibrating to national or international standards. Such high standards require professional calibration technicians to do the job. They have the equipment and expertise needed to adhere to the proper procedure and ensure that your electronics will return reliable outputs.
The Process of Calibration
When it comes to how engineers calibrate electronics, the exact steps depend on the type of equipment. However, the process does include basic activities such as choosing a standard, testing, calibrating and reporting.
1. Choosing a Standard
When it comes to testing equipment and calibrating it, the first step is choosing a standard. Numerous standards exist, from those used by a particular calibration shop to international standards. Though a calibrator does not need to use international standards for testing equipment, they do need to have measurements that trace back up to national or international standards.
For example, the shop standards need to align to secondary standards, which compare to primary standards, which in turn correlate to national standards from the NIST, which meet international standards. Though this tracing involves many steps, its critical trait is its unbroken chain from the measurements used to compare equipment at the shop to those set forth by international and national standards organizations.
During the testing phase, the engineer tests the electronics you need calibrated against a test sample of a known amount. Depending on the equipment and how you use the electronics, engineers may use one of several testing options
Individual instrument testing and calibrating involve examining and adjusting each electronic separate from the system it works in. Combining instruments and testing and calibrating them as a group is called loop calibrating. When checking all devices in an interconnected chain, if the results show output that measures out of tolerance, test individual tools. However, if the entire loop remains within tolerance, the individual devices should be, too.
Testing may also be bench or field. These types distinguish the location of the test. Bench testing occurs in the highly controlled environment of a shop and is ideal for calibrating new equipment before you install it in your facility. Since you have not established the device in your facility, you will not risk changing its accuracy through disconnecting it and sending it to the shop.
If you already have a piece of equipment in operation, field testing or on-site calibration may be a better option. This type of testing and calibrating occurs with the electronic equipment in its location. Choosing field calibration may require you to request on-site testing, but the results will be more accurate based on the device’s configuration and current situation. You also do not put the equipment at risk of impacts from removing and shipping it to a calibrator.
3. Calibrating the Electronics
Part of the testing process involves calibrating the device if the tests do not return perfect results. Engineers readily correct span and zero errors through calibration.
A zero error means the equipment does not measure correctly at its low end of measurements, or near zero. For instance, a scale with a zero error may read 32 grams when the weighing plate has nothing on it. Subsequently, all other readings will be 32 grams higher than the actual measurement. Zero errors occur when the line of output runs parallel to the graphed line of correct measurements. Adjusting the equipment moves the error line to match the right reading line.
While the zero adjustment moves the entire line to its correct position, the span error adjustment changes the line’s slope to match the accurate readings. This difference means that higher values measured with a span error will be farther away from the accurate values than smaller amounts. Because such differences affect readings across the span of the device’s use, calibrators must test several values from the low to the high end of the calibration range. Do not confuse the calibration range, or the amounts tested, with the instrument range, which is the lowest and highest amounts the equipment can measure.
Once the engineer correctly calibrates the equipment, they will create a report based on the standards used for calibration.
4. Reporting the Results
When it comes to the results, you should get either a hard copy or a digital version of the report. The information on this readout will be helpful if you have issues in the future with your equipment or if a problem requires you to prove that you had correctly calibrated electronics.
The report differs depending on the company that performed the calibration, but at MicronPA, we include the following on our long-form reports:
- Values before and after calibrating
- Date of inspection
- Name of the technician who calibrated the equipment
- Recommendation for the next service date
- Additional information for auditing purposes
Why You Should Outsource Electronic Calibration
Outsourcing electronic calibration should be your first option, not your last resort. By trusting a company that specializes in this field, you will spend less money, get the expertise required, save your employees time and ensure that your equipment adheres to strict regulatory standards.
Proper calibration requires some investment, but if you do not have a company that does the job correctly the first time, you will waste money. Consider calibrating your electronics to be a portion of your equipment maintenance costs.
Additionally, you can purchase lower-cost equipment and calibrate it to measure more accurately than the manufacturer designed it to. A professional calibrator can overcome the broad tolerance of some manufactured products and make adjustments to ensure they return more accurate results than initially built for. This option allows you to save money over time by reducing your equipment purchase costs.
Regardless of the quality or purchase price of your equipment, you will still need regular calibrating to ensure it works as intended, so why not save a little money on the initial cost of the device?
2. Expertise Required
Correctly calibrating electronic equipment requires extensive knowledge of how the device operates, what the standards require of it and how to make it more accurate. Now take all that knowledge and multiply it by the variety of electronics you have, and you will begin to appreciate the vast expertise required by professional calibrating technicians.
The technician you trust to calibrate your equipment must have the following traits to ensure they complete the job correctly:
- Attention to detail
- Exceptional documentation abilities
- Knowledge of a variety of testing processes and which to use for a situation
- Understanding of national and international regulations
If you do not have personnel on staff who are qualified to calibrate your equipment, you might consider training some of your employees to do so. However, this is an extremely time-intensive task, and it often makes more sense for companies to hire outside calibration professionals. Even if you already have employees who can do this job, outsourcing your calibrations frees them up for other projects central to your business’s operations.
Time is critical to every industry, and you may not have employees with enough available time to devote to properly calibrating all your electronics. Choosing to outsource this service will save your employees time, but only if the calibrating happens quickly. That’s why you should trust MicronPA. We offer on-site services for calibrations, and for other tasks, we have a fast turnaround time of five days. The less time your equipment needs to go out of operation for testing and calibrating, the less time your company loses.
4. Meeting Regulatory Standards
When it comes to regulatory standards, you need to have calibrators who know and will satisfy these. Do your employees have certification to calibrate to specific regulations?
At MicronPA, we hold accreditation from several entities:
- By PRI for ISO 9001:2015
- By the American Association for Laboratory Accreditation (A2LA) for International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) ISO/IEC 17025:2005(E)
- By A2LA for the American National Standards Institute (ANSI) and National Conference of Standards Laboratories (NCSL) ANSI/NCSL Z540-1-1994
- By A2LA for ANSI/NCSL Z540.3-2006
These credentials prove our commitment to holding up the strictest standards required of laboratories. With these credentials, you can trust our calibrations to be audit-worthy and reliable.
Connect With Us for Your Calibration Needs
When you need your electronic instruments to be accurate, trust us with their calibration. At MicronPA, we offer a large number of services to our clients in Pennsylvania, Virginia and Maryland, including free quotes, on-site calibration, fast turnaround times, and full accreditation. We also take individual care of our clients by offering prompt responses to our customers’ concerns.
To get the precision you demand, trust our professionals to do the job to the exacting standards of ASTM, ASME and ANSI. We offer calibration for a wide variety of device types and will provide you with a long-form certificate with information about the process and when you need to service your equipment next. For more information about our services or to get a free quote, contact us at MicronPA.