It is a constant battle, but one that is necessary. Instruments consist of two basic parts, the sensor and the transmitter, but they don’t have to have a transmitter and if they don’t, then it is called a local instrument. An instrument is judged by its accuracy and this can only be maintained with routine calibration, as over time all measuring devices will degrade, which is usually caused by normal wear and tear. But shit happens and they can end up being damaged, changing their accuracy, and this could be from electric or mechanical shock or from them being placed in a hazardous manufacturing environment. Depending on the type of instrument and the environment in which it is being used, it may degrade very quickly or over a long period of time. Calibrating an instrument will ensure its reliability, thus allowing you to trust its readings.
Calibration is when you make comparison between a known measurement (called the standard) and the measurement using your instrument. Let’s say it is a temperature instrument and you know that ice freezes at 32 ℉ and that water boils at 212 ℉, then you would use these two points to check how well your instrument is working. There is always going to be some error, and that is why instruments have a permissible range of error. A measurement error is the difference between a measured value of quantity and its true value. Measurement errors occur more frequently the longer the device is in operation, so instruments are usually calibrated according to a preventive maintenance schedule.
I worked as an Instrument Engineer in several pharmaceutical manufacturing plants and although I was never required to calibrate any instruments, I did have to write procedures for the instrument technicians to follow, and I also had to review their calibration reports and record any relevant information on the computer system. In case any of the measurements were outside the permissible range, the device would need to be readjusted, or taken out of service. Bad equipment would lead to inaccurate results and the FDA was always looking at everything related to these instruments, because the only way a process could be controlled to achieve repeatable results is by having all of the instrumentation properly calibrated. In order for the pharmaceutical companies to stay in business making their drugs, they needed to have on-going instrument calibration performed routinely. Only a product that is kept within the established parameters is able to be sold and if it goes outside these boundaries, the whole batch must be dumped and that means no profit and more paperwork.
Written for Linda G. Hill’s Stream of Consciousness Saturday where this week’s prompt is “cal”.