I wanted to share a great discussion going on over in the ISA - International Society of Automation LinkedIn group. The thread is, Are there any effects of radiations by using wireless instruments in plant?Are there any government regulations?
Emerson's Dan Daugherty provides several points including the latest one in the thread:
One follow-up comment about antennas in close proximity: I have seen WirelessHART devices, perhaps about 100 of them all sitting on the same lab bench, all commissioned in network with no detectable loss of communication occurring. The very low duty cycle (e.g. 10 ms of transmission every 4-16 seconds) combined with frequency hopping takes the probability of collision down to a very low number. The interference we are concerned about is WirelessHART device in close proximity to a strong source such as a plant radio base station or repeater. In such cases, the concern is WirelessHART being drowned out by the plant radio, but no such worries in reverse direction.
In such instances, we recommend vertical separation of about 6 feet, and in some cases, placing low pass filters on the plant radio antenna (especially for the 450 MHz radios).