I would like is to share experience and knowledge through this article. This was based on my experience. In this article, I wouldn’t explain the basic concept of wireless. There are a lot of good sources if you want to learn wireless transmitters.
The authors will not be responsible for any loss or damage arising out of or resulting from a defect, error or omission in this document or from any users use or reliance on this document.
This article does not attempt to detail minor differences between WirelessHART and ISA100Wireless devices; nor features specific to the vendor; nor provides exhaustive studies of integration with various host systems.
Anyway, the manufacturer’s instructions on the use of any commercial product must be followed at all times, even if in conflict with the information in this publication.
The objective is to offer another system which has similar to wirelessHART/ISA100wireless. It can be considered as another option for a wireless system. It is a combination between wire and wireless but eliminating the high-price part .e.g multipair cable, variation cable tray size.
The reason I say it similar is based on several factors :
- Same standard technology in antenna.
- It is possible to use Mesh topology although different standards as wirelessHART / ISA100Wireless.
- It doesn’t require a Programmable Logic Controller (PLC) to manage and retrieve the data. It could directly retrieve by Human Machine Interface(HMI).
Wireless networks offer highly flexibility installation for existing building and offshore platform structures. Henceforth, wireless significantly reduces installation costs. In certain occasion, installation of sensor/transmitter will encounter difficult to hook-up which require a lot of scaffolding, no possibility to lay cable tray and cable due to road crossing or separate location by road/sea, etc.
During my early career as Instrument and Control System Design engineer, I always design with the most sophisticated and latest product. Thus, sometimes I overlooked at potential problem on maintenance and spare part.
Now, as I have more experience and more involve with different departments, I’m able to look broader views and long term problems.
In example, one of the long-term problems of wireless is providing spare batteries for wireless transmitters. In country which import batteries from the origin manufacture country, mostly there are 2 main problems
- Price, some country will not allow to purchase directly from the manufacturer. It has to purchase from the official distributor on that country. The problem emerges if there is only one sole agent. Price often determines by the sole agent not the market.
- Delivery time, usually it takes at least 10-12 weeks.
In addition to resolve the delivery time, battery is purchase in advance, but issue of self-discharge and aging should be considered.
Let’s start with the limitation scope of design
- Area coverage hundreds meter, WLAN (wireless local area network)
- Quantity IO around 10-15 Analogue Input
- Remote location meaning there are no or minimum habitat
- Only monitoring without supervisory control thus update rate is not essential.
The system architecture is as following
The equipment list as following:
- Conventional Transmitter, 4-20mA, e.g. Endress Hauser, Yokogawa, Rosemount
- IO logik E1200 Series , Moxa
- Transmitter, Power Beam antenna, Ubiquiti
- Receiver, Omni antenna, Ubiquiti
- Industrial Ethernet Switch, unmanageable
- Desktop PC with Reliance as HMI application
Actually, we have try with 2 ea power beam antenna and 1 ea omni antenna. Even the PLC as client as well, we don’t find any latency issue.
Another additional feature is to use Programmable Logic Controller (PLC). The system architecture could be as following.
Basically, PLC is not mandatory if the application is for monitoring only, unless there is something to control.
If PLC will be utilized, there are two option of logical network
At the first option, PLC as repository data then HMI (Operator Station) will retrieve all data from PLC.
At the second option, there two client simultaneously, PLC and HMI are requesting to Ethernet remote IO.
I use the second option since the remote IO logic E1200 is able to send data in real (floating type). Both HMI and PLC retrieve data in floating type 32-bit. PLC is installed for future development.
All IP is configured based on Private IP Addresses Class C
The first option (figure 1) mostly will be benefit if
- The protocol between PLC and HMI and PLC to field device is different, e.g., PLC and HMI is Ethernet I/P while PLC and remote IO Logik is modbus TCP
- Redundant HMI
- More than 1 client control station
I. IO Logik E1200 Series
The IoLogik E1200 series is Industrial Ethernet remote I/O. It has two embedded Ethernet switch ports that allow information to flow to another local Ethernet device or connect to the next IOLogik in a daisy-chain. More detail could be find in the link
It has 8 AI channel. AI input range has 2 mode. Voltage mode (V) and Current Mode (mA).
Scaling from 4-20mA to engineering unit could be enabled on the device.
If the auto scaling is enabled you don’t need to obtain the raw data. Result of scaling in real type data (Floating point) available from the modbus address. Data format is
II. Antenna, Transmitter and Receiver
The Wi-Fi antenna has capability to support modbus TCP protocol. As this application is using modusTCP, You will need to change the web server mode, server port from 70 to 502 to open the modbus TCP port. The other setting is left to default. Both Transmitter and Receiver have the same configuration.
For information, there are server port list could be configured based on well-known and registered port numbers for particular practice as shown table below.
I haven’t yet trial for Ethernet/IP protocol.
Since it using ModbusTCP protocol, arrangement order of double word should be aware when requesting a known floating-point value from the slave. Modbus itself does not define a floating point data type but it is widely accepted that it implements 32-bit floating point data using the IEEE-754 standard. However, the IEEE standard has no clear cut definition of byte order of the data payload. Therefore the most important consideration when dealing with 32-bit data is that data is addressed in the proper order. I’m using reliance product HMI to display the correct value on HMI, it need to swap byte and swap word. You could find more detail on regulation of IEEE modbus floating 32bit data.
IV. 1 Cost
The scale of project is one of the key factors for cost justification of wireless into a project. Design Engineers should assess and incorporate the following factors in their project cost estimating calculation model:
- Reduced engineering costs
Wi-Fi + Ethernet remote I/O could not fully eliminated engineering cost for :
- Tray and cable routing
- Detail support cable tray
- Cable schedule
- Remote IOLink wiring diagram
Meanwhile wireless system could be eliminated pertaining cable drawings and documents. In the other hand, other engineering document should be submitted such as
- Identify the necessary update rate of each WirelessHART/ISA100Wireless device to meet the specifications of the application as well as battery life.
- Determine the capacity of the gateway determined by the maximum update rate to be used in the network
- Use the following calculation to determine the number of gateways.
- Reduced labor
Both Wi-Fi+Ethernet remote IO and wireless system is significant to reduce labor cost.
- Reduced materials and material cost
It is possible that the main materials of Wi-Fi + Ethernet remote IO could be selected with a much lower cost than a wireless system. Although Wi-Fi + Ethernet remote IO still needs to utilize cable trays and cable but it has reduced significant material such as
- Multi-pair instrument cable is not necessary.
- More uniform of cable tray size
- Cable gland with uniform size
One of advantage using Wi-Fi+Etherent remote IO is the flexibility to select the product. Wide range product of conventional 4-20mA transmitter as well as wide range product of Industrial Ethernet remote I/O / Gateways. If you have tight budget you could consider this option. Henceforth, with carefully design it is able to obtain overall cost lower than Wireless system.
Below are typical of material list for Wi-Fi +Ethernet Remote IO + Transmitters (This is only example for comparison)
Below are typical of material WirelessHART (This is only example for comparison )
Below are typical of material ISA100Wireless (This is only example for comparison )
IV. 2 Antenna
Wi-Fi antenna and Wireless transmitter antenna basically have the same method as following
- Frequency band 2.4-2.5 GHz Instrument Scientific Medical (ISM) band
- Standard modulation 802.11g
Note: Wi-Fi antenna is covering all transmitters while wireless transmitter antenna is dedicated. Therefore you should assess the location of transmitter in order to obtain the acceptable gain and able to select the antenna.
- WirelessHART/WirelessISA100 use omni directional antenna to support Mesh topological.
The selected Power beam and Omni antenna use standard modulation 802.11g
IV. 3 Topology
The main difference is the ISO protocol stack at Level 1 and 2 which address by standards IEEE 802.15.4 for ZigBee, ISA100Wireless, WirelessHART, WIA-PA, and several others. Each of these standards has added its own upper-layer protocols to suit applications in many different markets.
WirelessHART/Wireless ISA use the newest technology and most revolutionary form of network is called a mesh. In a mesh network each station is both an end device and a network forwarding element. Mesh networks are naturally self-healing and redundant—exactly the properties
needed for industrial automation networks.
IV. 4 Security
ISA100 Wireless and WirelessHART posses built-in security. This will be differ with Wi-Fi where You need to specify how level safety of the system. At minimum, firewall need to be installed on the Host (operator work station).
However, based on my assessment for this system. In this installation, the location was remote, by means the location is far from the resident. It will be obvious and suspicious when unrecognized person around that area.
The process plant are surrounded by fence with radius define using method of restricted area.
The system is still localized, not connected to any other company network (business network). Hence this system is sufficient.
V. References and Bibliography
Dick Caro, “Wireless Networks for Industrial Automation”, 2014
Emerson Process Management, “IEC 62591 WirelessHART System Engineering Guide, Revision 3.0”,2012