Fluorescent lamps generate radiation components in the infrared range, which can be received by infrared (IR) receivers. If this radiation component, for example in electronic control gear (ECG), is modulated with the operating frequency of ECGs of ca. 25 kHz - 60 kHz, infrared controls with information frequencies of similar scales can no longer distinguish between wanted signals and signals emitted by the fluorescent lamp (see figure). This occurs particularly in high-sensitivity infrared receivers. In such cases, even the minor portions of infrared radiation emitted by fluorescent lamps can cause misinformation in an IR receiver. This may affect e.g. wireless headphones, IR remote controls, sound signal transmissions and paging system equipment.
Compatibility with IR remote controls
Figure 3.191: Disturbance of an IR receiver
- Fluorescent lamps emit IR radiation.
- The IR radiation is modulated with the operating frequency of the ECG.
- IR emitters, e.g. remote controls, send modulated signals.
- Where the modulation frequency of the signal (ca.) corresponds to the operating frequency of the ECG, this causes disturbance.
- The signal is covered by the noise signal and can not be detected.
Chapter "Healthcare sector", section "IR control in the OR" points to possible issues of this nature.
Where luminaires for fluorescent lamps are utilised, it is therefore important to opt for operating frequencies in ECG that differ from information frequencies in IR controls when selecting luminaires.
If the European standard EN 61920 "Infrared free air applications" and the respective frequency ranges of ECGs (see also table) are considered, such issues can usually be avoided. In case of doubt, preliminary testing for correct functioning of IR controls is recommended.
Table 3.138: Examples for operating frequencies of IR controls in the operating theatre as well as electronic control gear (ECG)
The most effective course of action is an appropriate selection of working frequencies for IR installations. For IR remote controls, transmission methods with sufficiently high carrier frequencies (over 400 kHz) should be selected. Likewise, the selection of high carrier frequencies can ensure safe operation in sound signal transmissions and paging systems. Here, frequencies of 2.3 MHz and beyond should be selected.
Another measure for avoiding IR control impacts caused by lighting, the infrared reception equipment can be positioned in a way that prevents directly incident fluorescent lamp light on the IR receiver.
When using LED luminaires, this issue does not occur, since neither infrared radiation nor light carrier frequencies in the aforementioned critical frequency ranges are generated.