Field instrument is divided into two categories--detecting instrument and actuator which are essential basic components of automatic system.  The selection of field instrument is related to stability and safety of chemical production. Therefor the misunderstanding of field instrument selection can not be ignored.

Detecting instrument includes temperature detector, pressure detector, flow detector, liquid level detector, and composition analyzer. Actuator is comprised of pneumatic actuator, electrical converter, valve positioner, and electric actuator. 

When selecting flow detector, we are likely to have the following misunderstanding: 

The more expensive, the better.

There are generally tow reasons for high cost flow detector: the way the manufacturer set price; the production quantity is small, so manufacturer has to increase price to ensure profit. 

Have blind belief in one flow detector manufacturer.

Some customers consider both parties have well established understanding with a manufacturer after they have purchased from this manufacturer. But they do not know instrument is also a family composed of nearly a hundred of types of products. Almost no flow detector manufacturer can declare that they can produce any type of flow detector. This can be clear from their price and after sales service. 

Only have interest in new type of flow detector

Do not be misled by salesperson. They are taking you as experiment. Even if it is qualified before factory, but is it still workable after long term operation? Can it satisfy your needs? The upgrading of flow detector is not as fast as that of mobile and TV. Old model is proved to be reliable by market. 

Only select models according to pipes

This is most likely to happen. The result is that measuring result is likely not reliable. It is not because the flow detector has quality problem. Flow detector is also a measuring instrument with its own measuring range. 

Model selection is not subject to medium type.

Although this does not often happen, but I have seen vortex flow meter is used to detect slurry. 

Some irresponsible manufacturer may tell you their flow meter is suitable for measurement of any type of medium. Do not believe it.

Installation does not meet requirement.

Many flow detectors require enough room for front and rear straight pipe. Before installation please read manual carefully to avoid unnecessary trouble. 

Do not set parameters after installation.

This is likely to happen to the flow detector with battery power supply. It is set before factory, so it is applicable as soon as it is installed. This may result in big measurement error and unnecessary loss. 

Do not maintain regularly.

This will lead to accuracy decrease of flow detector. You can ask your supplier how to maintain. It is like a car which needs regular maintenance after being driven for a period of time.