So a HART wireless standard was released a couple weeks ago. What's this mean to me?

My vendors are shrugging their shoulders, "too early to tell . . . ."

Maybe someone in cyberland has had a sneak peak at what the HART standard will mean to me.

Here's what I'd like to know.

Will a set (a couple of transceivers) of wireless radio boxes be available that can connect directly to a standard analog HART transmitter, take the 4-20 with HART riding on it, and back at the control room provide the 4-20 with HART riding on it? Sort of like the way we do it today, but without the wires between the controller and the transmitter.

And (this is a biggie) will I be able to use my old 275 or 375 or Siemens PDM (assuming we're smart enough to have the right DD's for whatever we're connecting to) to change URV or zero the transmitter, over the wireless radios?

Or will the HART wireless standard force me and all the rest of us to buy the newly released 475 that is 'HART wireless compatible' because the old stuff doesn't work on new HART wireless standard?

Any one have a clue out there?

Issac

 

See the August and Septwmber issues of Control, available in downloadable PDF format at http://www.controlglobal.com. The first has a "fieldguide to industrial wireless" and the second has the first official WirelessHART handbook.

WirelessHART will allow you to buy a wireless transmitter. It will also allow you to buy an adaptor to turn any or all of your existing HART transmitters wireless...and that adaptor can be located anywhere on the loop you want--not just right at the transmitter.

You will be able to use any and all of your HART tools on HART 7 transmitters, whether they are wireless or not.

Check out the information above-- any more questions, just ask.

Walt Boyes
Editor-in-chief
Control magazine
www.controlglobal.com
Sent from my BlackBerry® wireless device

 

You should have come to the ISA show in Houston a few weeks ago to see the HART booth... The ISA show continues to be the launch pad of choice for new technology.

Final products will come early 2008 but you could see several brands of different kinds of WiHART equipment and software in the booth.

You could see wireless transmitters with the radio, antenna, and battery lasting several years built-in. For this solution there is no more 4-20 mA, its pure digital.

They showed gateways (access points) for the control room end. They talk Modbus and OPC just like wired HART multiplexers.

You could also see WiHART adapter for 4-20 mA devices. It's a radio that sits at the device. With this solution you use wired HART devices as usual. But instead of wiring up a multiplexer to get data into your asset management system, the wireless adapter and the gateway gets the data into your asset management system without wires.

I did not see any box that converts WiHART back to 4-20 mA although I am sure it is possible to make such a thing. However, I personally believe that using Modbus or OPC to digitally integrate the gateway to your control system is a better solution. Modbus and OPC are universally acceptable so no need to convert back to analog.

WiHART devices must have wired terminals as well so all your existing tools can be used as-is hooking up the old fashioned way, e.g. 375. WiHART gateways and interfaces on display emulate wired HART multiplexers and interfaces so your PC software cannot tell the difference. You can continue to use DD software as usual, although DD is now called EDDL since IEC standardization in 2004. EDDL now includes graphical enhancements that makes it easier to use and applicable to more sophisticated devices (see www.eddl.org). PDM was on display as well.

HART provided a very smooth transition from 4-20 mA to digital. Looks like they have done it again...

Budget for a small scale trial in 2008.

Cheers,
Jonas

 

Why use WiHart adapters for existing Hart transmitters in the field with radio, etc. if we can use Hart Mpx-ers installed in control rooms, as usual? No any cable saving, as cables are already existing.

Please suggest me!

 

Your observation is correct. For several years, HART multiplexers have been available to collect the digital data from HART instruments in the control room. They are wired to the same termination points on the Analog Inputs for the DCS or PLC, or often in a cable marshalling room where the HART circuit is connected to a power supply. The connecting pair from the HART instrument 4-20 mA line is connect in parallel across these terminals for each instrument connected to the
multiplexer. HART multiplexers scan across each of the input HART signals and buffer the digital data at the time of sampling.

Therefore, the data from the multiplexer is not real-time but is close to real-time. Users seem to avoid the use of devices not made by their DCS suppliers. The wiring cost of HART multiplexers and their capital cost also seem to inhibit their use.

WirelessHART does not need a multiplexer. The data is continuously sampled and may be sent to a DCS or PLC on demand or on schedule. Although it is not as fast as the 4-20 mA signal (nothing digital can be that fast) is much faster than the wired HART digital data, and is suitable for control of some loops. This is equally true of native WirelessHART instruments or wired HART instruments with a WirelessHART adapter.

ISA100.11a, when it is done early next year, will work in the same way with instruments designed for that wireless standard, and for adapters that convert wired HART instruments to the ISA100.11a network.

Dick Caro
===========================================
Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,
2 Beth Circle, Acton, MA 01720
Tel: +1.978.635.9449 Mobile: +.978.764.4728
Fax: +1.978.246.1270
E-mail: [email protected]

 

Many, maybe most, legacy control rooms either cannot take the output from a HART multiplexer or there is no room to install HART multiplexers. Many DCSes were installed without HART Multiplexers. The real issue is the difference in cost between installing HART multiplexers and using WirelessHART on existing systems. On new systems, WirelessHART is significantly less costly, and based on testing so far, about 99.99% reliable. If that is reliable enough for your control system, it is definitely something to consider.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
Mailto:[email protected]
Read my blog SoundOFF!! At www.controlglobal.com/soundoff

 

My question: What is the reason to use wireless adapters and gateways for existing and cabled into control rooms HART signals instead of simple and standard low cost HART multiplexers?

I do not see any advantage:
- cables are existing
- wiring works are required also for adapters, not just for multiplexers, most adequate to install radio adapters in control room, where no Ex-protection required -- but why transmit with radio on distance 10 meters?
- radio communication is less secure comparing to cables
- no advantage in communication speed (and speed is not really important for Access management)

I do not see any advantage to use wireless against wired multiplexer applications.