High-tech drug manufacturers are utilizing Industry 4.0 technology to enhance their automated processes. Portable mixing tanks used in drug processing, preparation, material buffering, and storage are sometimes fitted with multiple industrial sensors to ensure the highest standards in drug production are always met. The data generated during these processes can be transmitted wirelessly to the process control system with the help of Pepperl+Fuchs’ Bullet WirelessHART adapters.
When to use which WirelessHART adapter?
Transmitting small amounts of data over long distances is one of the challenges in process plants. With WirelessHART technology, this can be done efficiently: communicating field signals wirelessly saves time and reduces costs while enabling consistent and safe communication between the field and control side—even in large-scale plants.
Variable delays can be an issue in process automation applications where the need is for continuous operation. Improved wireless adaptors combined with a new HART command can help you maintain control. It’s all in the timing.
What is WirelessHART?
WirelessHART is a wireless communication network designed especially for sensors used in process automation. It connects individual sensors to a distributed control system (DCS) or asset management system.
The Internet of Things is an up-and-coming technology which is set to transform the way we live. Simply put, it allows machines to communicate directly with each other over the Internet. This connection between machines will lead to greater convenience and efficiency based on a more rapid exchange of information. Everyday examples might include a car telling a garage door when to open or close, a stove turning itself on to boil a pot of tea that will be ready for you when you come home from work, a timer setting thermostats, and your refrigerator letting you know when you’re running low on groceries.
In a previous blog post, "General Characteristics of HART Communication", I went over the important aspects of HART, which is a wired communication technology that has been in existence since the 1980s. Naturally, technology does progress, and just like telephones moving from land lines to wireless, wired HART is moving to WirelessHART. Let's explore what you should know about WirelessHART, and what improvements it can offer to your plant communication.
Highway Addressable Remote Transducer
HART is a digital signal that rides on a standard 4 mA ... 20 mA process control loop. In the field of process automation, the 4 mA ... 20 mA loop is very steady. You may hear of it being referred to as “quasi-static,” as it doesn't change much. Field devices like mass flow, temperature, pressure transmitters, or valve positioners use this 4 mA ... 20 mA signal. HART information is extra information that you get back from your field instruments.
Historically, HART communication uses the BELL 202 telephone communication standard, which telephone land lines still use today. This standard was introduced in the early 1980s and uses Frequency Shift Keying (FSK) technology. FSK simply means that the information is keyed or coded into the frequency, which is how the data communicates back and forth. HART layers its digital communication signals on top of the 4 mA ... 20 mA control signal.
A drawback based on today's standards is the speed of HART communication, which is rather slow. HART is limited to 1200 bits/second and ranges from 1200 Hz to 2200 Hz. Information (1, 0) is represented by different frequencies. The HART signal creates 0s and 1s. A logic 1 is represented by 1200 Hz. A logic 0 is represented by 2200 Hz. On the plus side, HART communication doesn't interrupt the 4 mA ... 20 mA signal, and it allows a host application (master) to get up to three digital updates per second from a field device.
Back in the day when this technology was introduced, 1200 baud was screaming fast, but now it is painfully slow and just doesn't measure up to our expectations. As an example, a LAN (Local Area Network), in common use today, perks along at 100 Mbits/second. That's 1000 times faster than the BELL 202!
If the communication speeds are so slow, why do we continue to use HART communication for field instruments and devices? Well, the 4 mA ... 20 mA control signals with FSK are reliable and have been in use for decades. There is a large installed base of devices. By our estimates, there are at least 30 million HART-compatible field devices in use worldwide.
Also, the HART information is easily extracted without interfering with the 4 mA … 20 mA signal used by the host system. Host systems are most commonly a distributed control system (DCS), programmable logic controller (PLC), asset management system, safety system, or a handheld device. HART enables two-way field communication to take place and makes it possible for additional information beyond the normal process variable to be communicated to or from a smart field instrument.
They are vanishing at alarming rates, and often times it goes unnoticed. They are disappearing everywhere, from phones and computers to vacuum cleaners and speakers. They are wires and they are on the verge of extinction!
WirelessHART antennas, integrating WirelessHART equipment from other manufacturers...
Are you ready to learn more about WirelessHART? This is our third installment of Ask an Expert, and our first episode to focus on WirelessHART. Basically, we sit down with a product expert and answer questions from customers like you.