Fundas of Measurement and Control…….

In an August afternoon a 3^rd year, 5^th semester instrumentation engineering class was going on in an engineering college. From the total strength of 90 students most were present but their minds were out of the class. The head of the department who was a former scientist in RRL, Bhubaneswar was giving an introductory lecture on measurement science. He asked the class, “What do you measure with a clinical thermometer?” Many voices were heard. But all the voices had the same answer. Some said, “Temperature”, other refined the previous answer and said, “Body temperature”. The tall body of the HOD was standing near the black board and he shook his head. He said, “No”. Every body was amazed. There was a murmuring. He continued, “In clinical thermometer (not talking about digital thermometer) often called mercury thermometer we measure the length of mercury column which is in some way or the other related to the body temperature. Measurement is all about comparison of a measured quantity with the international standard of the same quantity.” Some of the students stared at the HOD in an unbelieving eye realizing the simplicity of the answer and again murmuring was heard. This time it was some what loud. Some students discussed it among themselves. This is a simple fact, but we miss the finer point many a times. The class continued with the HOD describing about qualitative and quantitative measurements and wound up the class.

A year later, one of the students who were present in that class was having a chat with one of his friends in a hot March 24^th 2006 afternoon over a simple lunch of “Pakhal”, the Oriya trademark dish of watered rice eaten during the summer.

A (Friend): “Now that your girl friend got a lucrative job offer from software MNC how are you feeling?”

B (Student): “I am happy but can’t say how much happy I am.”

A (Friend): “Why not?”

B (Student): “As an instrumentation engineer we are thought to measure different parameters. We just measure them using some methods and compare them with the standard to get the measured value. But we don’t have any tool to measure the happiness neither has a standard for happiness. So I am happy.”

A couple of years later the same student who started his career as a lecturer in an engineering college asked the same question to the class and to many other people. He got the same response as given in that class and the same shocking response from the individuals when the answer was finally told. But the real dilemma is that there are international standards set for each and every measurement (be it length, weight, flow, pressure etc etc) but no standards are there for human emotions. The units may differ like pounds in Europe, US, kg in India. The quantity of product you get by asking 1kg potato to the shop keeper is the same in Amsterdam and in Amritsar. You can measure the potatoes but not the pain which is killing you. You can just take some medication which can help you to reduce the pain.

Technically speaking “control” is a step by step phenomenon adapted to keep a physical/chemical/mechanical parameter under a desired reference value despite of variations in operating conditions. There are different parameters in a process like pressure, temperature; flow etc and all these parameters have to be kept under a reference set point. But in real life we loose our control over very small issues. Once we loose our control and get angry than all the system of our body goes down and it takes nearly 45 minutes to get back to normal situation. The control action varies from person to person and time to time. Some people can easily be calmed down where as others take much longer time to calm down and control their desires and feelings. The control action also depends on the situation and it is time varying in nature.

Though we don’t have any fixed set point for measurement and control of physiological parameter like pain, happiness, sorrow, anger, greed we can very well control it using our attitude towards life and our past experience. It can be stated that only I am talking about some traits of human which are discussed above and those can’t be measured and neither can be controlled. But all other physiological parameters like heart beat, pulse beat, respiration, cardio vascular parameters can be very well measured using advanced biomedical instruments and controlled by your physician.