Experiment 01 with IR indicators:

Direct detection of 880 nm LED radiation

This experiment describes the fundamental application of the IR indicators IRI 1100 and IRI 1400 for testing 880 nm IR LEDs.

Required equipment

IR source: 880 nm LED (eg SFH 485 from Siemens)
IR indicator: IRI 1100 or 1400
Daylight source or UV-A fluorescent lamp (eg bill detector; only IRI 1400)

Safety measures

Shortwave UV radiation decreases the life span of the indicator card and may harm eyes! Use UV absorbing sunglasses!

Preparation: Charging

Expose the IRI 1100 or 1400 to daylight or fluorescent light prior to use (charge). The charging time depends on the intensity of the exciting light. Normally, it takes less than a minute. Important is the blue part of the charging light. The IRI 1400 may also be charged by UV-A radiation. In this case it shows a visible green fluorescence. Incandescent bulbs are inappropriate because of their high IR level. They would discharge the card simultaneously during charging.

Realization: IR detection

Hold the active area of the IR indicator card near the light emitting diode with ambient light shielded or in darkness. If there is IR radiation, the active surface will emit visible light (IRI 1100: orange; IRI 1400: green). To distinguish between IR stimulated emission and self discharge glowing (IRI 1400) switch the IR source on and off. As soon as the IR stimulated emission decreases, recharge as desribed above.