Smart instrument


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I am working as a instrument engineer in Ocean Development dept of Govt of India. Can you please me the basic technical difference between an ordinary instrumentation and a smart

-- vedachalam.
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Bhajanpreet Singh

In Smart instrumentation, digital signal is super-imposed on conventional 4-20mA analog signal. This digital signal can then be used in various ways by the manufacturer. Most commonly used is calibrating the instrument to various ranges without actually going in the field. Smart instruments can also give diagnostic help to the engineer and some instruments can directly be connected to plant's DCS for calibration and diagnosis.

Diana C Bouchard

Sorry for the delay, there is often dead time involved in my answering A-list messages, especially over the holidays. As I understand it, the distinction between "smart" and conventional ("dumb") instruments is not 0/1, but rather there is a continuum of "intelligence". A completely "dumb" instrument just burps out (on a display, over a wire, ...) what its sensor element saw. A slightly more intelligent one will e.g. perform compensation (temperature, humidity, etc.), adjust range and zero, detect obvious faults in itself. A more intelligent one will do e.g. units conversion or other calculations based on the reading, and more sophisticated fault detection and self diagnosis. A *really* smart instrument (e.g. a fieldbus device) will be able to initiate/respond to complex network communications, describe its own status to a controller, etc.

The real question is: what kind of intelligence do you need, and how much? Here's where some instrumentation vendors will have a field day with you. Many ads describe anything above the "completely dumb" level as a "smart instrument". This means about as much as describing vegetables as "organic". Define your needs, then do research and ask questions to make
sure you're getting what you want.

Diana Bouchard

Diana C. Bouchard
Pulp and Paper Research Institute of Canada (Paprican)
Process Control Group
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