A few more questions (with answers) from the recent wireless webinar:
Q: Are there any wireless devices designed specifically for Hazardous Locations (XP, IS, NI, approvals)? Are there any special considerations when using a wireless device in a HazLoc?
Yes, there are currently access points and solutions available for hazardous locations, but most of these are single vendor or proprietary solutions. The mainstream PLC and market vendors have not released wireless solutions for Hazloc’s up to now, but these are upcoming. So finding the right products for a complete PLC / IO application right now is difficult. Expect these to be coming in the near future and more product choices.
Q: Can you elaborate on non-overlapping channels?
Within the 2.4 GHz band are specific channels used for the radio frequencies (2399.5 MHz – 2424.5 MHz is Channel 1 and 2404.5 MHz – 2429.5 MHz is Channel 2 and so on; note the overlap 04.5 – 24.5). For 802.11b there are 11 channels used with 5 MHz separating these channels. If channels are too close together it can cause interference from the overlapping / crosstalk between the channels. This won’t necessarily cause the communications to fail, but will slow it down due to retries. So it is recommended to use channel separation (non-overlapping channels) when you have access points on different frequencies in close vicinity to each other. The recommended best procedure is to use Channel 1, 6, and 11 with 802.11b. With 802.11a you have a lot more non overlapping channels (8 or more depending on country) and more flexibility.