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I've used the WebRelay, and the people who make it have a catalog of control-via-web stuff. But although I can find analog inputs, digital outputs and digital inputs, I find no analog output. http://www.controlbyweb.com/product_catalog_12.6v1.0.pdf Maybe it's in development?

4-5 years ago I stopped by the Modbus booth at the national ISA show. I told the booth guy that I'd done a fair amount of work with various Modbus RTU or TCP devices with HMI and SCADA systems, but then asked him what the deal was with Modbus Plus because I never run into it. His...

A colleague used a Red Lion Data Station Plus (DIN rail mount control module with serial and ethernet connections) with its integral web server to manually control an Advantech analog output over a network. Red Lion also has a Modular Control Master (CSMSTRZR) has an integral web server...

This 7 minute video on youtube, Reflected waves on a cable, shows the distorted waveform on an oscilloscope as energy is reflected back from an open or a shorted length of cable, which helps explain the phenomenon of reflections. A resistance inserted which matches the load clean ups the...

I've heard that the US nuclear power industry is served by some companies that reverse engineer and manufacture devices and instruments from the 1970's and then put them through the nuke qualification process. You could look for an engineering firm to do the same and be able to skip the...

> maybe there was something wrong with the mechanical transmission between the turbine and the total flow indicator. The turbine meters that I'm familiar with are mechanical turbines, but electronic pick-ups and electronic flow indicators. Do you have a meter that is strictly mechanical...

If your existing analog input module does not support either - your types of RTDs, or - generic resistance measurement that can be either converted to a 4-20mA/Profibus/FoundationFieldbus signal and then characterized/linearized/function-generated/look-up-tabled in the DCS or...

FYI, a year ago, maybe two years ago, a forum topic involved diminishing air pressure in a closed column over water. The consensus seemed to be the air was absorbed gradually by the water. So you've got temperature compensation and air loss by absorption to deal with. (I can't recall which forum...

The Modbus Standard Modbus over Serial Line V1.02 (downloadable for free at Modbus.org) says: The format ( 11 bits ) for each byte in RTU mode is: Bit order per Byte: 1 start bit 8 data bits, least significant bit sent first 1 bit for parity completion 1 stop bit The requirement for...

2 wire RS-485 is implemented differently from manufacturer to manufacturer. Although you might have (+) to (+) and (-) to (-), one might have been labeled the opposite of the other. If wired 'backwards', it won't damage the drivers, but the 485 link won't work. Try swapping the...

1) Have you tried looking at more than one data format? 2) Have you tried reading from another starting value, one higher or lower than what you are using now? The manual on the web http://energy.te.com/china/crompton_doc/Integra%201630%20Communications%20Guide%20Iss%204.pdf (take out...

The link below is to a Chipkin's "Modbus for Field Technicians" document that covers Modbus pretty well, it's worth a look through. www.chipkin.com/files/liz/MODBUS_2010Nov12.pdf It's specific to their stuff, but their explanations are pretty good. Some PLCs support Modbus 'natively', as...

What is the "top side" connection"? dry leg? wet leg? capillary with a diaphragm seal? Which port is which? High side at the bottom? Low side at the bottom? What is the process temperature of 'scalding' juice at the diaphragm of the transmitter? Is the system under constant...

A frequent control.com contributor, Walt Boyes, is author of an excellent instrumentation book, Instrumentation Reference Book, now in its 4th (?) edition. For instrument technicians, an open source free book (which undergoes frequent updating) is Lessons in Industrial Instrumentation by Tny...

You can read Liptak's comment on loop diagrams for smart instruments here: http://www.controlglobal.com/articles/2013/ate-liptak-pauto-smart-instruments.html?CMP=ILC-rss take out any space characters the forum software inserts into the URL

Key term: Instrument Loop Diagram http://iamechatronics.com/notes/general-engineering/231-instrumentation-documents-loop-diagrams take out any space characters the forum software inserts into the URL

Installing Instrumentation on Insulated Bearings http://www.ge-mcs.com/download/orbit-archives/2001-2005/1st_quarter_2001/1q01nurcombe.pdf (remove any space characters the forum software inserts into the URL)

http://iamechatronics.com/notes/general-engineering/294-h1-foundation-fieldbus-physical-layer

Curt, Those L&N's you remember are probably not that much different from the one on display at the Smithsonian, representative of the one used to record background microwave radiation now considered residual big-bang remnants. http://airandspace.si.edu/collections/artifact.cfm?id=A19970342000

The data in the slave/server (presumably data in the PLC?) is in a format that has to be interpreted by the master/client (DCS?), which means both the master and the slave need to use and handle exactly the same data format. 32 bit words can be one of several formats: -32 bit long integer...