1. Primary instrument and secondary instrument are idioms used in instrument installation engineering. The exact name should be measuring instrument and display instrument. The measuring instrument is in direct contact with the medium and is installed on-site outdoors, while the display instrument is mostly installed on the control room panel. In order to distinguish the instruments in a set of systems, the instruments installed on-site are referred to as primary instruments, and the panel-mounted display instruments are referred to as secondary instruments. The professional interpretation of the secondary instrument is an instrument that accepts electrical or gas signals sent by transmitters, converters, sensors (including thermocouples, thermal resistances), etc., and indicates the measured value of the process process parameters. Take the real object for example, such as digital display meter, temperature control and so on.
2. Primary instruments are used to directly detect equipment, such as radar level gauges, pressure transmitters, flow meters, thermocouples, and so on. The secondary instrument means that the analog signal measured by the primary instrument is processed by the secondary instrument, and the correct value can be displayed intuitively. Secondary instruments are generally digital instruments, recorders, etc.
Simply put: the primary meter belongs to the signal acquisition conversion (various transmitters, temperature components, signal acquisition equipment), the secondary meter displays the alarm adjustment (panel display alarm instrument, input of the distributed control system, input of the distributed control system) The problem comes from the automation control instrument. Example picture:
The main differences between the primary instrument and the secondary instrument are:
1. Different in nature
One time meter:
In the production process, the measuring instrument is often called qualitatively according to the number of energy conversions, and the instrument is called once when the energy is converted once.
Secondary instrument:
In the production process, the measuring instrument can be converted twice as a secondary instrument.
Two, the characteristics are different
One time meter:
Equipped with sensing elements to sense the changes of the measured medium parameters. Or have a ruler to indicate the reading; or without a ruler, it does not indicate the reading.
Secondary instrument:
Usually powered by a power source, there are two types of indications: analog or digital. The instructions are clear and the accuracy is high.
Three, the role is different
One time meter:
The function is to feel the change of the measured medium parameters.
Secondary instrument:
Used to indicate, record or calculate the measurement results from a meter.
Fourth, the installation is different
One time meter:
The installation location should be selected where the process parameters change sensitively and are representative.
Secondary instrument:
The secondary instrument is installed on the control panel far away from the process pipeline or equipment.
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