	Displacement Sensors

Hints on Correct Use

Measuring thickness and height differences

The use of two sensor units enables easy and accurate measurement of thickness and height differences of a target. The absolute value of a measured thickness can be displayed when the sensors are used in combination with the RD Series Analog Sensor Controller.

A.Thickness measurement
(X + Y)

B.Height difference measurement
(X - Y)

Set-up for measuring height differences or thickness

Eccentricity and vibration measurement

Eccentricity and vibration can be measured using hold functions to retain the analog outputs detected for a predetermined duration, and then processing these outputs.

Timing and output diagram for eccentricity measurement

1)	Peak hold	The highest input value in the operation cycle is retained. * The displacement sensor is designed to generate a higher input voltage when measuring a target at a longer distance. Thus, the sensor retains the value of the deepest (shortest, thinnest) portion of a target.
2)	Bottom hold	The lowest value in the operation cycle is retained.
3)	Peak-to-peak hold	The value obtained by subtracting the lowest input (bottom) value from the highest input (peak) value is retained.

Connection to external equipment

Digital meter relays, pen recorders, and other equipment having an impedance of 1 to 100 MΩ are easily affected by external noise. To prevent the sensor from malfunctioning due to external noise, follow the guidelines given below.

Countermeasures

1.Use a shielded output cable.

The shielded cable can be extended to approximately 10 m. To further extend the cable, use a current transformer or A/D converter.

2.Use a twisted-pair cable.

*	Isolate the sensor wiring from power lines and high-voltage lines to prevent a malfunction due to noise interference.

Switch-selectable response time and resolution

The response time is dependent on the capacitance of the capacitor within the circuit. When the capacitor is set for a response time of 20 ms, it has a greater capacitance than when set for 0.7 ms.

For high-accuracy measurement

Select a low response time. (Note: This will reduce responsivity.)

For high-speed response

Select a high response time. (Note: This will reduce resolution.)
Analog voltage output in relation to displacement and response time.

Chart of Switch-selectable response time and resolution

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