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Proximity Sensors: Noise and Noise Countermeasures

FAQ No. FAQ00417

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Question

Please teach the malfunction of the Proximity Sensor by the noise and the noise measures.

Answer

There is a possibility of taking the influence of the noise by various pathways in the proximity sensor, and the malfunction mode changes depending on the frequency band and the level of the noise.

Typical examples of the malfunction are as follows;

(1) Output chattering

(2) It remains the state when the sensor detects the object regardless of the presence of the sensing object.

(2) It remains the state when the sensor detects the object regardless of the presence of the sensing object.

1. Understanding of malfunction occurrence (quantification)

(1) Occurrence frequency

(2) The malfunction mode

(3) Is all numbers generated?

(4) Is not there environmental influence?

2. Identification of noise source

(1) To identify of which pathway noise it is.

(2) Is there relation between operation of specific equipment and the malfunction of the sensor?

3. Measures not to put out noise

(1) The power equipment and frame ground of the control equipment are surely grounded.

4. Measures not to receive noise

(1) It wires the power line away from the signal line (wiring for the sensor).

(2) Please examine the following measures.

Noise measures method

When it invades from the noise source through the mounting (metal)

1) The inverter motor and the mounting metal are grounded.

2) The noise source and the power supply (0V) are grounded with the capacitor.

3) Insulators such as rubbers and resins are put between the sensor and the mounting (metal).

When it invades the sensor directly after propagates air from the noise source

1) The shield plate is put between the sensor and the noise source (switching power supply).

2) The setting distance of the sensor is separated from the noise source to the place without the influence.

When it invades from the power supply line

1) The capacitor, the noise filter and the varistor are put between power supply lines (between + V and 0V).