Help in wireless network application

[toma743]

I am currently working on a project where I use a SLC5/05 at the remote end. I need to transmit the data over the wireless network to a control room(PC).
The SCADA/HMI is present in the control room. I have looked through a lot of wireless products however all require a "line of sight" to be operational.
The big problem is that I have a huge metal Tank in between the remote location and the control room. Can anyone suggest me which products might be useful? Does any one have a solution for this problem?

 

[seaston_65]

I'm under the impression that when it states "Line of Sight" all it means is that the spec range is only valid if you don't have anything in the way. I'm sure you can go through the tank, it'll just hurt your range.
This is all on the basis that in my previous apartment, I was getting wireless through the concret walls, just my signal wasn't full strength even though I was less than 30 ft from the router.

 

[mordred]

Correct however radio waves bounce on surfaces this causes the loss of range however it will go around equipment including concrete depending on its strength and thickness. This is due the the radio waves penetration. In better words the combination of the radio waves to pentrate some solid objects and and the reflective waves still able to be understood this will compensate for the point to point blockage also helps reduce range loss in most relatively open areas

 

[rguimond]

I am currently working on a project where I use a SLC5/05 at the remote end. I need to transmit the data over the wireless network to a control room(PC).
The SCADA/HMI is present in the control room. I have looked through a lot of wireless products however all require a "line of sight" to be operational.
The big problem is that I have a huge metal Tank in between the remote location and the control room. Can anyone suggest me which products might be useful? Does any one have a solution for this problem?

I assume you're looking at unlicensed band radios.

If speed isn't an issue (and it usually isn't, unless you're reading hundreds of points per second), try getting wireless equipment that operates @ 900 MHz - better penetration. 2.4 GHz is OK, but 5.8 GHz is quite poor at getting around & through obstacles.

 

[mordred]

the 802.11 standards works fairly well around objects as well

 

[Stephen Luft]

Is the metal tank a "solid" impediment...meaning there is no way that the waves can pass around the tank?

As was mentioned before, waves will bounce.

Here is a suggestion for a product that we distribute.

http://www.eternity-sales.com/Westermo/Industrialwireless.htm

There are both 900 MHz and 2.4 GHz that utilizes the 802.11 standard.

When meeting with the vendor this week, the topic of line of site came up. They were able to show a scenario whereby with two antennas they were able to transmit a signal through a solid concrete wall that didn't offer line of site.

The manuals are available for download as well, for your review.

Hope this helps.

If you have any questions, feel free to post or email me directly.

God Bless,

 

[mordred]

One side note experience has taught me the 802.11 standard has better reception than than the 2.4 standard also that 802.11 B and 802.11 G tends to encounter difficulties but the resons is still under investigation lol.

 

[mordred]

Forgot to add Omron though beams are also reliable in particular through beam. Another trick thats handy with the through beam type is the ability to use an increased sensing distance to gain greater sensing strength. When I size up the distance for these type I usually add 25% sensing range. This helps compensate for coating effects due to humidity or other coating affects

 

[Ken Roach]

I've seen this sort of thing done three ways:

1. Put in 802.11 b/g/n WiFi gear and hope for the best.
2. Put in 900 MHz industrial IP gear and hope for the best.
3. Have a site survey done by an experienced wireless consultant and put in the gear he or she recommends.

Somewhere in the middle is what I do in my own life; I am a member of a community wireless ISP at my residential marina and we have some challenging WiFi environment issues to deal with. One of them is a two-story steel-sheathed houseboat that completely shadows the inland half of Dock A. The surrounding structures are largely radio-transparent; the upper decks of wooden houseboats and the masts and rigging of sailboats, plus the trees and mud hillside of Gas Works Park. The only radio reflectors are the hulls of the tugboat Sea Witch and the derelict trawler Pacific Empire, but their angle bounces the WiFi signal out across the lake rather than inland to the places we need it.

In the WISP, we use inexpensive "mesh" repeaters to get a signal down the central dock to the shadowed slips. These are the least reliable of the WISP infrastructure devices and the throughput and reliability there stinks.

You might have enough radio reflective buildings or structures to get a decent signal on the other side of the tank, or you might not. The only way to tell for sure is to do a radio survey. This has the added benefit of telling you what kind of other devices are already operating in the frequencies you intend to use.

I have a nice and inexpensive 2.4 GHz analyzer from MetaGeek called the WiSpy, and it has allowed me to plan the 802.11 channels that we operate the WISP on. We know how crowded the 2.4 GHz spectrum is in the neighborhood, and when a powerful WISP started up across the lake and flooded Channel 1 with signal, we were able to move to Channels 6 and 11 effectively.

If you can't do a professional radio survey, I would go with a simple repeater (not a cheap "mesh" device) mounted somewhere that has a view of both sides of the tank. For industrial 900 MHz gear, my choice is Data-Linc 6200E and 6210E, and for commercial-grade WiFi gear I am an enthusiastic user of Ubiquiti Networks NanoStation and PicoStation hardware. The AirOS that Ubiquiti uses inside all their hardware is head and shoulders more reliable and stable than anything you're going to find in a consumer-grade WiFi access point from Linksys/Cisco or Netgear.

 

[sidsule]

Among the wireless devices the Zigbee is currently a very user-friendly protocol which is gaining popularity in the wireless network market.
I could suggest finding some Zigbee wireless device since using a the slaves in series makes it possible to overcome the problem that you are facing. Even though the Zigbee mentions that you need to have a line of sight you could use the following network topology to solve your problem.

http://www.plctalk.net/qanda/attachment.php?attachmentid=13271&stc=1&d=1269882481

The following link shows the Zigbee Host:
http://www.icpdas-usa.com/zb_2550.html

and this one shows the slave
http://www.icpdas-usa.com/zb_2551.html

 

[Clay B.]

3. Have a site survey done by an experienced wireless consultant and put in the gear he or she recommends.

This in my opinion is the best method. While you see the tank there are other things you could be missing.

Get a consultant and set up a test rig. This will let you know exacly what you need to get the job done.

Plus while the consultant is there you can pick their brains and get a better understanding of what your dealing with.