There are different categories of mounting systems of electronic instruments in industries. They are categorized by the way they are intended to be used physically, resulting in certain types of construction:
- Site mounting.
- Panel mounting.
- Bench mounting.
- Rack mounting.
- Portable instruments.
Site Mounting:
Site mounting means it is the process of mount instrument close to the physical process.
Signal conditioners and data acquisition subsystems connected to transducers and actuators generate signals that are suitable for long distance transmission, possibly a few miles away to a central instrumentation and control system. Full computerized systems are also available for use in less hostile environments with rugged construction.
The main electronic circuit is on one printed circuit board mounted on pillars, connected to one of a variety of optional interface cards. The unit is easily bolted to a wall or the side of a machine.
Panel Mounting:
Panel mounting is a convenient way to construct a system is to mount the various instruments which require control or readout on a panel with the wiring and other system components protected inside a cabinet.
Features:
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The enclosure is an extruded aluminum tube.
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The internal construction is based on around five printed circuit boards soldering the electronic displays. The PCBs can be plugged together and easily replaced for maintenance.
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All user connections are at the rear, for permanent o semi-permanent installation.
Bench-mounting Instruments:
Instruments which require an external power source but a degree of portability are usually for benchtop operation. Size is important, since bench space is always in short supply.
Instruments in this category often have a wide range of controls and displays that require careful ergonomics attention.
- The user inputs are at the front for easy access.
- There is a large clear display for comfortable viewing
- The carrying handle doubles up as a tilt bar.
- It has modular internal construction with connectors for quick servicing.
Rack-mounting Instruments
Most large electronic instrumentation systems are constructed in 19-inch wide metal cabinets of variable height.
Large instruments are normally designed for bench or rack mounting which is supplied with optional brackets. Smaller modules can then be plugged into a 19-inch cabinet.
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The modules are standard Eurocard sizes and widths (DIN 41914 or IEC 297).
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The connectors are to DIN standard (DIN 41612).
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The subrack uses standard mechanical components and can be part of an instrumentation system that is much larger.
Portable Instruments:
Really portable devices are now common due to reduced electronic circuitry size and power consumption.
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Lightweight, low-cost molded plastic case
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Low-power CMOS circuitry and liquid crystal display (LCD).
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Battery power source gives long operating life.
Encapsulation
For severe conditions such as high vibration, a group of instruments can be encapsulated. This involves encapsulate them in a suitable material, commonly epoxy resin.
This keeps the components in a very safe position and also protects them against the atmosphere to which the instrument is exposed.
Some epoxies are strong up to 300ºC. At higher temperatures (450ºC) they are destroyed, allowing encapsulated components to be recovered if they are themselves heat resistant.