Smarter sensors - (not always all that Smart)

The advent of the smarter sensor has been a boon to the control and automation industries.  It has brought an increased ROI for many vendors and end users of industrial control and automation instruments that rely on sensors.

(The term smarter sensor used here is used loosely to define a set of enabling technologies that add or modify information from the sensor(a smarter sensor used here could be a temperature reading from any microprocessor's on-board sensor to a probe with on-board intelligence.))   

What does the smarter sensor bring to the table?

Many smarter sensors have some of the following general advantages among others over a plain sensor(one with no intermediate steps between the sensor and the monitoring instrument.):

1. A smarter sensor may have the ability to automatically set up the monitoring instrument for the type of sensor that is attached as well as setting up ranges for that sensor and other qualities of the measuring sensor(i.e. measurement tolerances, timing information, signal type . . .)

2. A smarter sensor may have the ability to re-calibrate itself under a set condition(i.e. restart, error, timed interval, preset event, or on-command . . .)

3. A smarter sensor may have the ability to report its operational status(i.e. failure, degraded performance, wear, replacement time . . .)

4. A smarter sensor may have the ability to identify itself uniquely to the monitoring instrument by digitally identifying itself.  This adds the advantage of trace-ability to the sensor and sensor data.

5. A smarter sensor may have the ability to connect to communication networks such as the web or direct buses or cell phone/messaging or other networks to communicate information(i.e. alarm status,  failure status, process status/goal progress . . .) 

These advantages make the smarter sensors of today and tomorrow easier to use and provide more information to the end user.

However, there are applications where a smarter sensor(with built in intelligence) is not as desirable as a plain sensor(direct measurement) and a plain sensor has advantages over a smarter sensor.

Usually:

1. A plain sensor must be attached to monitoring instrument that is designed specifically to handle that sensor input.

2. A plain sensor must be setup and configured on the monitoring instrument by a qualified engineer or technician(there is a better chance the sensors will be properly placed and tested in a unique setup resulting in higher quality measurement when qualified personnel set up the monitoring instrument and sensors.)

3. A plain sensor provides a direct measurement to the monitoring instrument not an interpreted measurement(aka: think analog signal versus digital data for the same measurement from a plain sensor versus a smarter sensor(not all smarter sensors do this.))

4. A plain sensor is attached to a monitoring instrument that must be calibrated to that sensor.  The calibration stays until qualified engineer or technician re-calibrates the monitoring instrument.

5. A plain sensor can be interchanged with any of its same type of plain sensor and can be verified on any monitoring instrument/test instrument that takes that sensor(e.g. many multi-meters on the market can measure a plain Thermocouple sensor through a direct Thermocouple input port.)

6. A plain sensor is usually less expensive than a smarter sensor.

7. A plain sensor has less parts to fail.

8. A plain sensor gives you pure signal just signal, no overhead or data overload(you know what you are getting.) 

While not having to allocate qualified engineering or technical personnel to setup and calibrate monitoring instruments with smarter sensors there can be some trade-offs for this advantage.

When considering using a monitoring instrumentation setup with plain sensors or smarter sensors understanding; the reliability, quality of data/signal, where interpretation of the signal happens(on the sensor or in the instrument), ease of use, sensor performance, sensor replace-ability - all of these factors may influence your decision.

The unique application for which you install your monitoring instruments and sensors and the demands and expectations on the information or the data that you get will help you determine whether smarter sensors or plain sensors are best.   

    


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