Simplifying Machine Control Sensors Analog Design

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Inductive analog sensors can be advantageous in the design of control systems of the machine. These sensors are particularly useful for applications requiring precision measurement and position detection, and for use in component coding. The final selection of a specific sensor, it is important to examine performance characteristics to the unit you choose is optimized to best suit the requirements of machine protection.

Inductive Machine Control
The sensors main reason why the industrial position with analog outputs are useful for system designers because of their ability to deny the need for discrete output switch. Instead of spending a quiet exit when an object reaches a certain distance from the face of the sensor, an analog sensor provides a variable output voltage and an output current proportional to the distance from the target sensor face.
Simplifying Machine Control Sensors Analog Design “Table 1 analog output signal of the sensor changes with the distance Source: Eaton ..”

This achievement is an ideal of analogue inductive sensor for applications that require precise position sensing and measurement. This type of functionality is very useful for an engineer end user the angular position of a rotating shaft to measure, for example. In designing an eccentric cam on the shaft and use the analog detector output proportional to the distance on the ridge, the designer can calculate the position of the axis.

In another application, such as inductive sensors analog deflection supervision of an essential element. For example, these sensors measure the axial deformation of a rotating blade, the control system can be designed to reduce speed on the sensor output, which makes them significant damage to the machine of a deformed sheet.
analogue sensors can also be used for component verification error, the identification of a cylinder to divert much of rejecting, for example. In another application of quality control typical insertion depth of a specific set of fixation or a secondary part of a measure and a series of control measures are taken based on the results. In more advanced systems, the sensors can be used for statistical process control to provide information (eg changes in section thickness measured in time).

Because many large inductive analog sensors to sensor manufacturers in this category and they all look at how the performance characteristics of a specific issue of analog sensors do? Where are all the same inductive analog sensors?

Questions Linearity
To answer this question, it is important to understand what is meant by the term “linearity” as applied to the outputs of analog sensors. This is illustrated by the solid line in Table 1.

In other words, an analog sensor that is “linear” has the same extent by the division during the full scale of the device. That means 1 mm change in the position of the object results in the same change in output voltage and current, or when the target object is in the range of the sensor envelope. In this case, the solid line represents the output of an analog sensor “linear”.
Simplifying Machine Control Sensors Analog Design “Table 2 non-linear signal output analog remote sensor Source: Eaton ..”

The dotted line represents a sensor with a nonlinear response. Using a device with the output characteristic, January 1 mm change in range of the target when this target in the middle of the range of the sensor will result in a change in voltage or current output is very different from the magnitude of change observed with the target on one side of the gamma-band or another.

How will this impact linearity characteristic of the design of your control? Consider an application where a cutting tool is located on a metal part in rotation, the position of the cutting tool according to the measured thickness of the material. If the thickness of the material increases, the tool is withdrawn and drops as the thickness, the position of the tool is moved indoors. A non-linear inductive analog sensor with a maximum range of 10 mm, positioned to measure the thickness of the 0-10V supply voltage measurements analog shown in Table 2 using different thicknesses of the room.

As shown, position sensors with analog output nonlinear used in industrial applications must be applied with caution, because the non-linearity, system design and place restrictions on the physical application of the sensor is difficult for use in OEM equipment. Looking at this table, it is clearly a compensation signal processing will be needed to cope with the obvious non-linearity. Because non-linearity in this case non-uniform at both ends of the sensor performs a table is probably easier to implement a compensation equation. Anyway, the developer of PLC code even more complex and the response of the equipment can be reduced only temporary solutions are created to deal with the nonlinear nature of this sensor output.
Simplifying Machine Control Sensors Analog Design “Table 3 linear analog output signal from the remote sensor Source: Eaton ..”

In cases where performance in the picture is not reproducible, then the operating range of the sensor may need to be confined to the central part of the band in an attempt to more “linear” part of the performance curve presented in Table 1. This approach also has its disadvantages, such as sensors in question are often very limited range of detection. If the decision is no longer “linear” part of the nonlinear sensor used in Table 2, the designer has a wide window centered 3 mm to 5.5 mm to cooperate. Managing a small window of this size range may be impossible and the power of the Creator in a sensing technologies completely different.

Reduce complexity
So what is a control system designer to do? Take the example above, but using a sensor with linear output (see Table 3).

In this case, the task of control design is much easier. No lookup table. No fee equation. Simplified PLC logic. And since the range of the sensor can be used, it can be pulled further away from danger. For OEM customers, this means a greater availability machine and a higher throughput and Overall Equipment Effectiveness.

These examples show that linearity is an important characteristic of analog position sensors. Fortunately, a new approach for the design of analog position sensor have produced dramatic improvements in linearity. In addition, technological advances have allowed manufacturers of sensors greatly increased operating distances in the supply of analog devices. Taken together, these improvements in the design allows the designer to control much more flexibility in the implementation of analog sensors on a machine, and serve to reduce the complexity of a system.