Measurements are one of the fundamental necessities for progress. No scientific discovery would have been possible without the right instruments to measure data. Even in our daily life, measurements are unending: height, weight, distance, speed, time, and so on. This field, collectively, is known as Instrumentation.
"Instrumentation is a collective term for measuring instruments used for indicating, measuring and recording physical quantities.
The term instrumentation may refer to something as simple as direct reading thermometers or, when using many sensors, may become part of a complex Industrial control system in such as manufacturing industry, vehicles and transportation." -Wikipedia
If instrumentation is so vital in our daily lives, it doesn’t take a genius to guess how important it would be in the industrial sector. This gives rise to the field of Industrial Instrumentation.
But before that, let us take a brief look at the history of Instrumentation.
The term "Instrumentation" has been in use since the 19th century, though it's early usage was in context of musical instruments.
Before Instrumentation evolved as a field, there were simply measuring instruments. The most common entity that baffled humans since the beginning, was time. Hence, the earliest measuring devices were built to measure just that.
However, by the 18th century, instrumentation was everywhere. To undertake the vast array of inventions and discoveries, the need of precise measuring instruments arose, that could measure almost every entity: Pressure, Temperature, Density, Current, Voltage etc.
Industrial Instrumentation has been recognized has a critical necessity ever since the rise of automation in industries. The logic is simple: If one needs the machines to automatically perform operations without human supervision, then it follows that reliable measuring instruments must be present to give accurate readings of various conditions.
Let us have a look at the various entities that Industrial Instrumentation focus to operate upon:
Temperature: Temperature is perhaps the most important quantity as far as industrial production goes. Low temperature would yield no results, while high temperatures can lead to unfortunate accidents. This is why various techniques have been developed to accurately measure temperature. In small industries, temperature is usually at the medium range, so Resistance Temperature Detectors (RTD) are used. The difference in the wires (due to temperature) creates a voltage, which is then converted into digital reading.
Thermocouples are used in location that need more durable sensor, like those in steel plants.
Pressure: Pressure is another quantity, whose miscalculation can lead to enormous hazards. Thus, pressure in an industrial unit is carefully maintained. The technique used is relatively simple: Two tapping points are used; one connected to the line whose pressure is to be estimated, and the other connected to open air. The difference in pressure is then measured.
In industries like petrochemical, a Pressure to Current (P/I) Convertor is used. In it, the indicated pressure can be a digital or an analog form. The main advantage is that it can be directly shown on the control panel in the control room, thus enabling the human operators to keep a check on it. This is true for temperature measurement also.
Flow: The Flow of various raw materials is also important to know at various points of industrial process. Here, too, a transmitter is used like that in pressure measurement. But the difference is , the two impulse lines are connected directly to the line, and an orifice is used to create a differential. The amount of differential will vary and we can measure the flow with the help of Transmitter.
The generic term for such devices are “Flowmeters”. Flowmeters are generally of vortex, positive displacement (PD), differential pressure (DP), coriolis, and ultrasonic varieties.
Level: Level indicates the amount or stock of various quantities like water level etc. In case of materials like petroleum or natural case, it is very critical to maintain the right level throughout the production process.
The most common method of measuring level is similar to previous methods: two wires are tapped, with one wire connected to the lower part and other to the upper part; the difference is then used to measure the level.
Instrumentation, though, is not just restricted to measuring values. It is also responsible for providing the ability to modify some field parameters. That means the instrument is not only used for measuring purposes, but also for changing and modification of the process system, more commonly known as Actuators. In industries, actuators are used to regulate fluid, control flow, moderate temperatures and open/close electric circuits.
The latest improvement in the instrumentation technology has been the introduction of Intelligent Instruments.
Intelligent Instruments are called “intelligent”, because they can process the output of the initial measurements (with help of computers), thereby minimizing the chances of errors.
Some features of Intelligent Instruments are:
Signal damping with selectable time constants.
Switchable ranges (using several primary transducers within the instrument which each measure over a different range).
Switchable output units (e.g. display in Imperial or SI units).
Remote adjustment and control of instrument options from up to 1500 meters away via four-way, 20 mA signal lines.
With the rapid pace with which we are moving towards automation and advanced industrial production, Instrumentation will keep playing a vital role in industries.