Question: In our rapid assembly & test operations, multiple stations operate and report their status in-process to a central Server over an Ethernet network. The Server should communicate with the remote instrumentation at each station with updates in 10mSec max. Do you have any Remote I/O that can perform at this speed and minimize delays or loss of data on our network?
Answer: Although there are many factors that contribute to network speed, instrumentation internal scanning, processing and response times can be a major portion of this time. Our Ethernet XT series is engineered with PriorityChannel technology by Innovasic. Fieldbus protocols such as Modbus TCP/IP, Ethernet/IP and Profinet are treated as time-critical messages. This technology allows critical application data to get to/from the network without interference from other non-critical traffic. This means that protocol messages will be delivered on-time making the communications with the Remote I/O more deterministic. If two different Remote I/O products with identical 10mSec response times are compared, the product with PriorityChannel technology will perform reliably at faster polling rates and lower latency. The XT series includes many types of I/O models with updates for all channels in 10mSec or less.
Question: Our wastewater treatment plant has areas with corrosive atmospheres including chlorides and sulfides. Over time, these environments can degrade or damage sensitive electronics. Do you offer any protection for your products in these applications?
Answer: Yes, Acromag has an automated conformal coating process. This protection helps electronic instrumentation be resistant to corrosive areas, including salt and high humidity. Here is a video showing this service.
Question: At the Power Plant, we have a differential pressure (DP) transmitter with 4–20mA output measuring the pressure across an Orifice Plate. In peak demand cycles with extremely high loads, the DP output goes above 20mA. This is treated by our new DCS system as being a failure and is resetting a valve to the pump. This causes higher water flow with the Boilers that are making steam for the Turbine. The DP transmitter has to be scaled according to the Orifice Plate. It would take too much for us to replace the Orifice Plate and Suction Flow Piping. Instead, we would like to add a 4–20mA Transmitter at the front-end of the DCS that should clamp the DP output at 20mA. Do you have a product that can do this?
Answer: Yes, the 800C-SIP software program for our 811T-0500 Transmitter in the Intellipack Series has a 25 break-point linearizer. This can be used to characterize a curve that would clamp the output at 20mA when the input goes above 20mA. The transfer function can have one or two clamps to set minimum and maximum levels at any points over the full output range. This program can also be used to linearize a non-linear curve.
Question: Are there any alarm features in your Ethernet I/O? We have remote Robots with E-stops to monitor and local shut down is preferred if an instrument or system failure is detected.
Answer: Yes, in our EtherStax series, if any channel has an over temperature, over current or over voltage condition, the internal circuitry will shut down all channels to that port. Also, if the Ethernet connection to the unit is broken, then the watchdog timer trips and sends the outputs to pre-selected states. Plus, there is an onboard fail-safe relay that will change state with a lost Ethernet connection, watchdog timeout or loss of power.
For more information:
Question: What’s the best choice for a 4-20mA isolator to do both sinking output loop powered and sourced output connections?
Answer: The TT236-0600 is your best choice with Acromag because it is an isolated transmitter that can be wired for both sinking or sourcing outputs.
Question: What are the main reasons for using a signal splitter?
- The ability to drive more than one device
- If the two devices are far away from each other, then daisy-chaining the 4-20mA loop could create a ground loop or noise problems.
- If the sum of the input impedances of both devices requires a higher compliance Voltage than the Source Transmitter can handle, then the two outputs can provide more total gain.
- You could have two or more devices operating from different power supplies and it is desirable to keep their grounds separate.
Question: We have a large industrial campus with multiple gated entryways. We would like to remotely control the gates from the guard station. We do have a wireless Ethernet network available. Do you have a way to remotely control many 3 way switches to open, close & stop?
Answer: Using Acromag’s peer-to-peer i2o, switched inputs at the guard station will communicate over Ethernet with switched outputs at the gate. I2o also works with analogs and temperature inputs.
Question: We will be installing and data logging 12 flowmeters around our plant. Some with 4-20mA outputs and others with pulsed outputs. Is there a way to totalize the flows remotely over Ethernet so our DCS can simply read back the totalized flows periodically.
Answer: Yes, our 967EN-4008 and 989EN-4016 Ethernet Remote I/O can totalize and store the accumulated flows in non-volatile memory. The 967EN-4008 has 8 current inputs where each input is sampled every 8 mS then added. The 989EN-4016 has 16 DIO where 8 channels can be used as up or down counters. The remaining 8 channels can be output alarms for the associated counter inputs. Your DCS would communicate with the Remote I/O using Ethernet Modbus TCP/IP.
Question: In your product manuals, the wiring diagrams show to connect earth ground for best practice. What will happen if we do not connect earth ground?
Answer: In most industral applications, transient voltages and currents are present and are often conducted along the wired power and signal paths. If this energy is conducted into the instrument, it could create measurement errors or shorten the useful life of the product. The manuals indicate how to apply earth ground to the device and the I/O so that an alternate path is available to shunt or steer this energy to earth ground where it can be safely dissipated away from the instrument. For more information on proper grounding techinques, please see our whitepaper entitled “Electrical Ground Rules“
Question: I’m using the XT1221 to measure differential voltage signals with a range of 0-5VDC. I’ve set up my PLC scaling such that a Modbus count of 0 = 0V, and a Modbus count of 30000 = 5VDC. Our technician recently installed new XT1221 units, and now the values we are seeing in our PLC are about 2/3 of the actual signal values. What could be causing this?
Answer: All XT series analog Modbus modules have built-in legacy support, which is enabled by default. With legacy support turned on (YES), bipolar analog input ranges are normalized to ±20000 (unipolar is 0-20000). When legacy support is turned off (NO), bipolar analog input ranges are normalized to ±30000 (unipolar is 0-30000). Therefore, you must disable legacy support via the USB program of your XT unit so that the Modbus counts are scaled correctly in your PLC. This explains why you are seeing 2/3 of the actual value in your PLC.
Question: We have XT Series modules connected to our network with the IP address set and the channels configured. The EDS file has been installed and RSLinx Classic can see the modules. How do we connect to the module to scan it?
Answer: The first step is to program the XT modules via the provided software… you’ll need to program the network settings, I/O settings (Analog ranges for each channel and some digital settings for the DIO modules). Once this is done, you can use the appropriate EDS files to install the modules into your Studio 5000 (or RS Logix) software. An item of note when using the EDS files; once you setup the modules, go the general tab and change the module definitions:
- Electronic keying: Exact match
- Connections: Change from SINT to INT
Once you go online, take a look the PLC tags for each module. For the XT1222, it will show 16 tags, the first 8 of which are channels 1-8 input data. These are 16-bit signed integers. Range will be dependent on whether you have bipolar or unipolar inputs, and whether you have legacy or non-legacy enabled per channel (see user manual for descriptions). For the XT1112 module, it will show 5 tags, the first 4 of which are for channels 0-15, least 4 bits show the DIO state). See XT1112 manual.