Belt Scale Integrator Has Linguistic Talents

February 19, 2015

6 Min Read
Belt Scale Integrator Has Linguistic Talents
Control rooms represent the nucleus of process automation. The ability to be integrated into existing networks is crucial for easy installation.

Selling products into the process instrumentation and control field is like trying to have a conversation in the United Nations: you need to speak a lot of different languages.
Instruments and controllers can communicate using several different industrial protocols. Selecting a protocol depends on where you are in the world, what protocol your main system uses, what you are trying to communicate, and how fast you need to communicate.
Most facilities require some form of communication – long gone are the days of sending out a technician to read a display or copy down a total in a log book.
The information age is all around us, and instrumentation is no exception. Process values, data, and instrument states are all entered in a consolidated form into control systems where technicians sitting comfortably in climate-controlled rooms can easily access the data.

Talking the Talk
Weighing is a major part of the process instrumentation portfolio, along with level, flow, temperature, pressure, positioning, and analytics.
Some instruments are simple and only have a small amount of data to transmit. For example, a temperature sensor essentially only needs to transmit the temperature of some material or product. A huge amount of data is not required.
Others, like a belt scale integrator, can provide material flow rate, belt load, belt speed, total amount of product, alarming, PID control, and complete parameter access. That is where the Siemens Milltronics BW500 comes in, with its wide range of communication options.
The Siemens Milltronics BW500 features multiple standard and optional communication protocols:

• Standard: Modbus ASCII, Modbus RTU, 4-20mA, relays (two or five), two remote totalizer contacts (AC or DC)

• Optional: Profibus DP, Profinet, DeviceNet, Ethernet/IP, Modbus TCP/IP

And of course, you can use more than one protocol at a time. For example, Profinet could be used for integration into the plant automation system, while the 4-20 mA output could be used for a remote display at another point in the plant or for users to input data into another device.
The Siemens Milltronics BW500 is, after all, a belt scale integrator, and it is always recommended to have the integrator close to the scale for calibration. This means that a remote display could be installed some distance away from a stacker in an aggregate pit, for example – or perhaps even in another part of a plant.
Some of these protocols are more popular than others. In fact, one of the Siemens Milltronics BW500 protocols recently went into retirement because the Allen Bradley RIO automation system had been phased out. And with Ethernet being used more and more in home devices, it is also increasingly establishing itself in the industrial environment.
Let us take a more detailed look at some of these communication protocols and other methods for transferring information to discover just what the advantages and disadvantages really are.
• Relays: Fairly straightforward, these are switched on or off. Not a lot of smarts; however, the brilliance lies in their simplicity. Users can program setpoints in the Siemens Milltronics BW500 to trip relays controlling feed devices, to turn other machinery on or off or to control audible or visual alarms.
The use of relays should never be underestimated and with two relays as standard or optionally five, the Siemens Milltronics BW500 is well equipped.

• Totalizer contacts (AC or DC): There is really only one use for these and that is to provide an input to a remote totalizer – typically a continuous device such as an integrator or flow meter provides this type of functionality.
With a remote totalizer, you now have a reliable backup if your device is ever struck by lightning. In fact, many metrological approvals require their use. Having options for both AC and DC versions is ideal for any type of totalizer a customer may use.

• 4-20 mA: The most popular of all methods for communicating variables, the 4-20 mA (milliamp) signal is the primary process variable from the device. For a Siemens Milltronics BW500, this could show material flow rate, where 4 mA represents zero tons per hour and 20 mA represents the maximum tons per hour of the application. This can also be a 0 to 20 mA signal if desired.
This is simple to use and integrate into a control system, but it doesn’t provide any other data that the Siemens Milltronics BW500 has available: no speed, load, total, or device status at the same time.

• Modbus RTU/ASCII: Modbus is a very old protocol for exchanging data with the device, not just one-way data transmission. The Siemens Milltronics BW500 has both Modbus RTU and Modbus ASCII. Modbus ASCII is the older of the two and slower, but is not time dependent, and therefore works very well with modems.
Modbus RTU is slightly younger and popular for retrieving information from intelligent devices. In fact, there is no other protocol that is more widely supported than Modbus RTU. However, the lack of a detailed protocol standard has led to a number of variations in the protocols, which typically does not cause a problem when used in a point-to-point configuration.

• Modbus TCP/IP: An Ethernet-based protocol that is an open standard. Modbus TCP/IP is very easy to use and configure. It also has the advantage of not requiring any separate device files for integration. It is great for monitoring purposes. However, there is a processing delay because it uses the TCP/IP stack, which means that many do not consider Modbus TCP/IP to be a real-time protocol.

• Profibus DP: This is a fast protocol that has extremely good noise immunity and is also internationally standardized. It requires GSD files (Profibus database files) for device integration; however, it is popular and widely established.

• DeviceNet: Slower than Profibus, DeviceNet requires a five-conductor cable, which can increase connection costs. The protocol is primarily used by Allen Bradley for connecting devices to their PLCs, but it is also standardized by a governing body and has a high noise immunity.

• Profinet: The fastest of all the options and also the largest data throughput, Profinet is growing in popularity – you can expect this Ethernet-based protocol to overtake Profibus.

• Ethernet/IP: An open standard mostly used by Allen Bradley systems, Ethernet/IP is not as fast as Profinet and also needs ESD files for device integration. Ethernet/IP is primarily used in North America with Modbus TCP/IP.
Any protocol requiring a configuration file is available for simple integration and all of them have gone through rigorous testing in our development center to ensure reliable service.
With more than 10 different communication options, the Siemens Milltronics BW500 makes industrial communications easy.
    For more information, call 705-740-7024 or visit www.siemens.com/weighing.

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