DanW

I thought Q meant Q for Quelle, meaning "source", as in, outputs source current or voltage. Siemens' technical dictionary, Fachwörterbuch Energie- und Automatisierungstechnik, in the German English volume has Quelle f(Transistor: "Source")/ source n Dan

Zero-Day Exploit: Countdown to Darkness (Cyber-Fiction) The US version of Stuxnet.

The key term is heat/cool. Controllers that do heat/cool control, like a Honeywell UDC 2500 or 3200 have two outputs, one for heating, one for cooling. When running "duplex" mode (Honeywell's term for heat/cool) the controller is typically configured so that the heating band and the cooling band do not overlap. They also typically have two sets of PID constants, so that the heating loop can be tuned independently of the cooling loop. The Honeywells have a choice of PID (modulating control) or ON/OFF for either or both loops. I happen to prefer the Honeywells because the manual has 4 pages of instructions on running a duplex autotune under various conditions.

It might be prudent to check out the comments on Atlas Copco's implementation of a couple of their products here: http://www.plctalk.net/qanda/showthread.php?t=66720

1) How do you propose to control the roof door vent(s) ? Some sort of actuator is needed to position the vent/dampers/whatever. Is the door either fully open or fully closed so that a relay output either drives the door open or drives the door closed? 2) Cal Controls sells single loop on/off-PID temperature controllers. Cal had a Windows program some years ago, WIN 98 era, that would datalog the data from the controller (via RS-232, I think), show data as a trend and display a controller faceplate to show the current temperature. I don't know if CAL still offers the program. They also offered separately an OPC server, but OPC servers are not cheap (~$400 at the time) and there are no free ones. But an OPC server is worthless if you aren't running an OPC client. I am unaware of commercial DDE communications packages in the single loop world. The single loop controller world is huge, probably 50-100 vendors worldwide. I suspect other brands offer a low cost Windows data logging program. You're wrapped in data logging, but you might want to think about what the final control element action is going to look like. Maybe misting (turn a valve on) makes more sense?

It can be normal mode noise from electrical hash makers like flourescent lights, VFD's; or induced from AC wiring. It can be common mode noise with a very low limit common mode limit of 5V. Direct from the Automation Direct F2-04THM manual, 7-8, 7-9 Ungrounded Thermocouple Assembly An ungrounded thermocouple is electrically isolated fromthe protective case. If the case is electrically grounded it provides a low-impedance path for electrical noise to travel. The ungrounded thermocouple provides a more stable and accurate measurement in a noisy environment. Use shielded thermocouples whenever possible tominimize the presence of noise on the thermocouple wire. Ground the shield wire at one end only. For grounded thermocouples, connect the shield at the sensor end. For ungrounded thermocouples, connect the shield to the 0V (common) terminal. The DL205 base has a switching type power supply. As a result of switching noise, you may notice some instability in the analog input data if you use the base power supply. If this is unacceptable, you should try one of the following: 1. Use a separate linear power supply. 2. Connect the 24VDC common to the frame ground, which is the screw terminal marked "G" on the base. Unused temperature inputs should be shorted together and connected to common. WARNING: A thermocouple can become shorted to a high voltage potential. Because common terminals are internally connected together, whatever voltage potential exists on one thermocouple will exist on the other channels. Use shielded wiring and ground the shield at the transmitter source. Do not ground the shield at both the module and the source. Do not run the signal wiring next to large motors, high current switches, or transformers. This may cause noise problems. If the T/C signal is not noisy when it is hanging in the air (not connected to where it should be), then you have noise source or path from the device you want to connect to. I'd disconnect T-C's to see only one has little or no noise, then keep adding until I find the noisy one or two. Check the other stuff.

Thermocouples are not only a low level millivolt output but require 'cold junction compensation' because the look-up tables or polynomial equations used to calculate temperature from millivolts assume that the connection to the PLC input terminals is always at the freezing point of water (0°C, 32°F), yet the input terminal block is rarely, if ever, at that exact temperature. Without cold junction compensation the error can be in tens of degrees, the difference between the temperature of the terminal block at the PLC and the freezing point of water. There are two conventional ways of dealing with a thermocouple. a) Thermocouple input cards have 'cold junction compensation' built into them and the appropriate calculations to covert from mV to temperature for various types of thermocouples. These are supplied by the PLC vendor. Non-isolated models cost a lot less than isolated models. It pays to buy isolated. b) Thermocouple transmitter. These devices take a therocouple input and output a "high level" current or voltage proportional to the programmed temperature range. The device requires a DC power supply. Two wire transmitters have an external power supply in the same 2 wire circuit the provides the current signal to the PLC analog input. Non-isolated models cost a lot less than isolated models. It pays to buy isolated. A Google search for thermocouple transmitter will produce hundreds of vendors. If this is a one-off deal, be sure to limit your consideration to one that is either vendor pre-configured (free or some nominal fee) for the range you need or the software/cable to do so is really inexpensive because there are very inexpensive devices in this category where the cost to configure the output range is multiple times the cost of the transmitter.

If the valves are proportional modulating valves with smart positioners, the buried diagnostics in a HART smart positioner can be used to determine whether a valve is a likely prospect for re-build. The people who run commodity product on paper machines 24-7 where the profit is 21 minutes out of a 24 hour day use valve positioner diagnostics in just such a fashion -to minimize the relatively scarce labor during a scheduled outage. A given machine might have 36 valves on it, but only 14 might show enough cycling to warrant a rebuild during an outage. Every hour saved on an outage is money in the bank. Some use an asset management software program that reads and categorizes the HART diagnostics. Others use a HART handheld to read the data and fill in a spreadsheet from which they make their determinations. The 20 manual pages related to diagnostics for a Siemens positioner is attached so you can have a look see at they kind of data collected. I presume other brands have similar functions, but Siemens is the only one I'm familiar with. Siemens PS2 positioner diagnostics.pdf

To do any HMI/SCADA/Data acquistion you need to know what data is available, where the data resides, what the data format is and what protocol and hardware transport gives you access to that data. That kind of information is totally lacking on the main AtlasCopco web site. It appears to me that any connectivity that you might get comes from their optional HMI screen with datalogging http://www.atlascopco.us/Images/CDS0%201000%2024_tcm795-1700803.pdf Their color brochure says this option is an "Advanced Elektronikon® control and monitoring system, designed for integration in a (remote) process control system. What does Remote access mean? Just the web server built into it? Or are there publicly accessible tags and registers that could be read with an HMI program like Wonderware via OPC or an industrial protocol like Modbus or ethernet/IP? I don't have a clue how you'd find out, given that the Atlas Copco web site contains only the marketing information with technical substance along these lines. Maybe that information can be purchased. But that's the question - can you get the data needed from the various air compressors to make Wonderware do what it needs to do ?

> I have not come across many SBC based solution, but surely would like to see some.

You need to investigate which protocol is available on the 620 and whether you can handle the requirements of dealing with that specific protocol. Given the era, it might be raw ASCII, Modbus, or some proprietary protocol. If whatever protocol runs on a serial port, there are 'serial server' devices that convert serial to ethernet. But ethernet along is merely the carrier. Getting an ethernet card might not move your project any further along, unless you can deal with the communications protocol that's available.

I use a Mactek serial HART converter, too. According to whomever answered the Mactek tech support line (USA) about 2-3 months ago, HART comm will not work with a serial Mactek plugged into a USB-RS232 converter. I didn't go into details, I just accepted him at his word. You might call Mactek if you want details. Dan

This guy hangs around various fora advocating the Matrikon name. www.opcsupport.com Wassim Daoud Global Solutions Architect www.MatrikonOPC.com His typical response to specific questions, however is, "Please contact OPCSupport and they will be able to help you out. Visit here for contact info: www.opcsupport.com Given that Honeywell bought Matrikon over a year ago, one might think that Honeywell could point you directly to support for an OPC issue. Have you inquired of the Honeywell systems group?

I'm not clear what you're trying to do. To "source [a field instrument] to a manual component" means? Does it mean that the pressure transmitter value which now runs to the PLC needs to be displayed at the instrument or somewhere else, somewhere else being ______ ? An example or two? Are all the instruments on Profibus, or are some 4-20mA? Assuming the instruments are Profibus and you need remote displays, an easy and cheap way is to buy an analog output card (0-20/4-20mA) and feed out each needed process variable as a current signal to a conventional panel meter mounted wherever it is needed. There are also loop powered meters for a location that doesn't have line power for the meter.

The stuff described above involves Honeywell's DCS, about which I can't comment; I've never been involved with the DCS side. In the US, Honeywell has nothing that they, nor I would consider a PLC. The instrument division does have what they call a hybrid controller, what others call a PAC (Process Automation Controller), the HC900. It's designed primarily for PID control, not high speed discrete control. It looks like a PLC - rack mounted power supply, controller, modular I/O. Ethernet for multiple rack comm. Native Modbus TCP master/slave with the flexibility of either factory Modbus mapping or custom mapping. Its I/O is as robust as any other I've encountered and more than some (good noise isolation on AI's) and better than some others (universal AI's for T/C, RTD, or 4-20). Software is function block, no ladder, no scripting. Function blocks include stuff like slidewire feedback actuator drives that's very handy, when that's what's installed. One time development software purchase, no annual licensing, free firmware updates on the web. The HMI panel uses software that populates the tag data base in the HMI from the controller configuration. It'll never do motion control or run a bottling line, but for thermal processing, it covers all the bases, which what it appears to be designed for.

I don't have an answer to your question, but I can point out a market gap for Acromag. A wireless gateway collect data from a variety of analog field devices (wireless HART or others). The Wireless Gateway is a Modbus slave. End-user needs the wireless concept, but can't handle the output from the Gateway as Modbus (for whatever reason), he wants wired in-wired out, in other words, he wants an analog output for every analog field device. There's no single box that combines a Modbus master and a number of Acromag style AO's, where the Modbus master reads the gateway slave, fetches the gateway values, scales them (sometimes they're floats, sometimes they're integers/20 or whatever), writes the data values to the AO points and then does it all over again. And mounts on a DIN rail. Dan

The entire Modbus spec is available on-line, for free at Modbus.org. Issues regarding coding a Modbus app show up on the control.com forum, which is associated with Modbus.org. You might try posting there for input, with detail on what your specifics are, if this well runs dry. That was a well written summary, BillySmithde2

The expected 0.5% error on the 5 gallons of diverted flow is 0.025 gallons. However, the flow meter's error is a percentage of its instantaneous flow rate. The upstream meter passes 85 gallons over some period of time at the stated 0.1% error or ±0.085 gallons. The downstream meter passes 80 gallons over that same period of time at the stated 0.1% error or ±0.08 gallons. The diverted flow is the difference of upstream minus downstream = 5 gallons over that period of time. Even if the flowmeter errors are not in opposite directions, but the same direction, each flow meter's error based on percentage of flow rate is 3+ times the expected error of the diverted flow: - the upstream meter's error of ±0.085 gallons is 3.4 times the ±0.025 gallons expected error. - The downstream meter's error of 0.080 gallons is 3.2 times the ±0.025 gallons expected error on the diverted flow. At a total of 17 gallons of diverted flow, one approaches the point where the error approaches the expected 0.5% error. 0.5% of 17 gallons = 0.085 gal

You might try posting to the control.com forum because the forum is associated with Modbus.org and you mihgt get a response there.

Are you sure that the installed meters are Coriolis meters? for water service? I thought immedieately that they were vortex meters, because any vortex installtion faces a low flow drop out for the conditions you cite. The 5gpm diversion flow rate is less than 10% of the 80 gpm nominal flow rate and likely falls into the low velocity range in which vortices are not produced at a sufficient rate and the meter reading is forced to zero. All commercial Vortex meters have a low flow drop out for this reason.

I have. It works fine for current output signals (like a control output driving a valve), but can be tricky and sometimes not useable with loop powered, 2 wire field transmitters. For field devices, power is the issue. I found that I needed to try a DPDT relay, so that the unselected 4-20mA could be directed to a dummy load resistor to complete the 4-20mA circuit. Otherwise, the source device was unhappy, needing initialization time when to recover from a power down situation. I seem to recall a frantic search for make-before break contacts. But it was some years ago.

1) Many controls distributors run their own SI, service, or calibration groups. Others don't. Check out the distributors in your area and let those who don't have their own SI group that you're available for projects of whatever size you deem doable. 2) If you're looking for an excellent discussion of much of the details of project work, much of which is documentation, whether on the scope end or for the enduser, an ISA publication covers these topics pretty well. Successful Instrumentation and Control Systems Design by Michael Whitt is two distinct parts, one a paperback book, the other a CD with templates of many of the forms in the book.

Thanks. Very enjoyable.

The motion detector has to be rated for hazardous area use, explicitly saying so on its tag; including the specific areas, rated as Class x, Div y, etc, along with the agency (FM, typically in the US) that issued a hazardous area compliance approval. Those devices so approved for intrinsic safety have very explicit tables of I/S entity parameters printed in their manuals. The entity parameters are used to select an intrinsic barrier. If your motion detector does not have tagging indicating it is approved for I/S use, or the manual lacks the entity parameters for the device, the device is not rated for I/S use and it cannot be installed in a hazardous area.