EGE-Elektronik Spezial-Sensoren GmbH - Special-Sensors for Automation

Infrared detectors - Applications

Function and application

Where conventional sensors would fail due to too high temperature, infrared detectors working on a non-contact principle can be used. They respond to the radiated heat of the hot materials. Compact units with optics are used for distances of 2 to 8 m from the object. For distances of only a few cm, heat-resistant light-conducting cables should be used for transmission.

Series ODM

Infrared detectors ODM... detect energy radiated by a hot body in the near infrared range (1 ... 3 µm). Energy absor- bed within the spectral range determines detected temperatures. Optical and assessment electronics are situated in a stainless steel casing. O-ring gaskets ensure safe operation even in the presence of large temperature and humidity fluctuations. The plug connector is water tight to IP 68.
If environmental temperatures exceed 70° C, an optical fibre cable can be used up to 250° C. This can be fitted with a supplementary optical system if required. In case of such applications, the optical fibre cable should be laid in protective tubes and not be frequently moved.
The fibre cable fast-connector LLK-plug allows for fast and safe exchange.
The infrared detectors are specified for different sensitivities. If the target temperature exceeds the sensitivity specified, the output of the detector will be activated.

Series OD 100

The sensor OD 100 GSPP detects temperatures up  to 300°C contactlessly. Within this temperature range it is possible to adjust two switching points. The switching status is indicated by two colour LEDs. The sensor OD 100 GA has one analogue output 4.20mA. The temperature of an object detected by the infrared detector  depends  on  the  emission  coefficient,  the distance and the lighting area. To prevent these influences it is important to adjust the switching points of the infrared-detector on site.

Series ODE

The ODE 350 infrared sensor measures the energy transmitted from a body in the near infrared region (1 ... 3 µm). The energy taken up in this region of the spectrum is a measure of the temperature of the hot objekt. The device has four outputs which are independent of one another; two analogue outputs (current, voltage) and two outputs each with a switching threshold preselectable as either a relay change-over contact or as a semiconductor output. The required characteristic curve is preselected by a selector switch.

The device is operated using a fibre-optic cable, which can have temperature stability of up to 350 ºC. The standard cable can take up to 250 ºC. They have quick-release fastener provided with thread. To limit the angular field and increase sensitivity supplementary lenses for fibreoptic cable are available.

The given sensitivities refer to the use of a 1m long fibreoptic cable with a bundle diameter of 4mm during full illumination. Other fibre-optic cables and lenses yield correspondingly different minimum operating temperatures. As a rule, a fibre-optic cable with an additional length of 1m decreases the reaction sensitivity by 75 ºC.

Adjustment on switching detectors

1. Remove protection screw from the potentiometer.
2. The sensor must be mounted at its finally position.
3. Turn the screwdriver till the output switches (LED red).
Now the temperature is adjusted on which the infrared-detector responsed. The switching temperature can be increased if you turn the potentiometer clockwise.
4. Remount the protection screw.

Analogue temperature detection

The current output for the temperature is correct when:
a) the measured object has a homogeneous temperature and when its area has a minimum size of the sensor.s detection range (see path of the rays)
b) the emmision coefficient is Epsilon = 1 (black body).

At other cases the OD 100 GA measure a too low tempe rature. Therefore the OD 100 GA has a potentiometer for an adjustment.

Adjustment

1. Remove protection screw from the potentiometer.
2. The sensor must be mounted at is final position.
3. The actual temperature of the object must be known.
4. Turn  the  potentiometer  clockwise  until  the  output  current correspond with the object temperature (see output characteristics).

Approval for safety applications
Sensors for personal security must have a qualifification approval according to EN 954-1 and must be labeled accordingly. Sensors that are not labeled must not be used for applications of this kind.

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