Desai feels, “The user has to fix the periodicity after seeing the results for three to four consecutive calibrations. For example, if every year it is exactly the same or within limits, he can extend the periodicity. If every year it becomes worse and he has to adjust or write down the correction chart, he has to compress the schedule. Generally, electronic equipment periodicity is one year, while for mechanical items like micrometers it is six months. Very precision equipment may require three months. If the equipment undergoes any kind of repair, it has to be calibrated after repair.”
“Any equipment which has to sustain shocks, vibrations, violent change of temperature or pressure, gets disturbed. Hence the master is kept in the lab in an ideal environment. Masters that are used for on-site calibration and are subjected to vibrations and change in environment due to travelling or handling, are checked and corrected with masters in the labs after they come back to base,” explains Desai.
“Normally, manufacturers of electronic instruments specify accuracy for a period of time. It is advisable that a user maintains and follows the calibration schedule and gets instruments calibrated at regular intervals recommended by the manufacturer,” cites Kela.
Advancements in microprocessor and microcontroller technology, sensor technology along with an intelligent software algorithm and connectivity to computers have led to the development of a new feature called ‘self-calibration’ and ‘auto-tuning.’
“Today, test and measurement equipment are available with inbuilt calibration check points that can be used as reference points for getting a calibration done. Calibration in itself is the next big opportunity in the Indian test and measurements industry as there are very limited options available for the industry,” cites Manish Kwatra, CEO, MetroQ Instruments.
In-house calibration vs third-party labs
It’s an ongoing debate in many manufacturing as well as R&D organisations whether to have an internal calibration lab or outsource the calibration activity to an external accredited lab. There are situations where you may require to re-calibrate the equipment every day. It is totally subjective to the nature of organisation and use of measurement equipment.
“Whether you manage internally or externally, boils down to a business assessment. Large shops are likely to save money by outsourcing, while small installations may find it less expensive to manage it internally,” comments Keith Kidd, director-packet systems testing at Vizon Labs.
Calibration is a process and needs to be managed like any other activity in the organisation. Kidd adds, “Regardless of how one manages the calibration process, it is necessary to ensure that your training and controls for the calibration system are well known to all. The most likely hiccup with calibration is getting the organisation to follow the process, which takes discipline.”
Philip Wright, director at QSO, a weighing equipment and scale service company, explains a case of his customer for whom his company carried out scale and weighing equipment calibration twice a year. The organisation had its own test weights which were also calibrated on a yearly basis.
“We used to carry out the equipment calibrations and issue a certificate after completion of test once or twice a year. However, on a daily basis, at the start of every shift the operator using the equipment would place the required amount of the test weights onto the equipment as a check and, if necessary, re-calibrate the equipment himself,” he tells. You may be thinking what was the point in having an outside company come in and calibrate the equipment in the first place then. Well, it all boils down to that little bit of paper and traceability for the audits. Although test certificates are based on the accuracy at the time of test, if you feel the need to have more frequent checks then the more affordable way is to have a trained calibration technician and an in-house lab.
Every R&D firm must have reference equipment against which samples are checked to have confidence in the measurement. Desai says, “It has to be a standalone reference equipment that can be used for verification. Firms producing rotating machines, tacho generators and motors must have a master precision tachometer that does have valid calibration all the time. Firms producing temperature sensors must have a calibrator or master precision resistor thermometer to check against that. Mechanical gauges require master slip gauges to check the wear and tear on instruments that are used to measure the finished goods very often.”
“Test and measurement equipment distributors follow a mixed regime for calibration. They have their own calibrating equipment which are traceable to ERTL or NABL. Also, there is dependence on the respective OEM for calibration of their own brand equipment,” shares Kwatra.
Importance can’t be undermined
In today’s world of competition, the only differentiator for your product is quality, which cannot just be assumed. To produce quality equipment, you need measurements that are accurate, reliable and repeatable.
“Not only for all the manufacturing processes but also for R&D firms, it is necessary to use calibrated equipment to ensure reliability of results. Correctly performed calibration increases the productivity, optimises resources, and assures consistency, comparability and compatibility of products, services and acceptability,” says Kela.
The importance of calibration cannot be undermined by any user. When performing any type of measurement, you must have confidence in your results that they are accurate and within specifications. Testing and measurement with calibrated equipment brings this confidence and is a form of quality assurance.
“There are many labs in India which provide calibration certificate and help maintain the accuracy of equipment. It’s just the matter of awareness at all the levels,” says Goliya.
The author is a senior technology journalist at EFY