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The way it is described, it sounds like an RS-232-to-RS-485 converter, where the RS-232 port has a DB-9 connector. One normally thinks of a telephone link when the word modem is used because the analog phone side uses modulated tones. If the device is in reality an RS232-485 converter...

Read chapter 5 http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf (take out any space(s) in the URL)

You are aware of the F4 comm manual at http://www.watlow.com/downloads/en/manuals/f4pdce_a.pdf 1) Download the MODBUS APPLICATION PROTOCOL SPECIFICATION V1.1b from Modbus.org 2) Page 4 shows the basic structure of a Modbus message: slave address, function code, address (range), CRC...

No experience, but I looked at the CR10x manual and it appears pretty straightforward Modbus. - runs Modbus RTU, not Modbus ASCII - supports function 03 read holding registers (does not 04 support read input registers) - floating point (FP) format - input locations 1, 2, 3 are in...

Modbus addressing generally starts at zero, with the register at address zero being register one, hence the 'one-offset' issue with Modbus. But the usage of terminology is not consistent between vendors, so some vendors call addresses 'registers' or vice versa, or use only one of the terms...

I'm surprised that you found a Modbus PCI card, I've never heard of one. I've added serial cards to PCs to get additional serial network links, but a Modbus card? I suspect that you mean adding a serial RS-485 PCI card to move the hardware comm link to an internal card, rather than a USB...

If you're talking about the documents needed to get the project working, then the tasks are to - setup the communications channel (RS-485, RS-232, ethernet, serial server, phone modem, whatever) - access the data register locations on the slave(s)/server(s) - deal with any data retrieved...

> Are RTDs simply a 'known' resistance/temperature profile? Yes, an RTD is an element that has a very well defined temperature/resistance profile. The main reason RTDs are used rather than thermocouples is inherent accuracy. But to achieve that accuracy, the resistance of the lead wire must...

Is it possible, no, 2 RTD's in series is not the way commercial RTD analog inputs function. One RTD per analog input. Each RTD is isolated from any other RTD or ground.

Watlow has quite an assortment of reference material linked from the F4 page: http://www.watlow.com/products/controllers/series-f4-process-controller.cfm?famid=15 Comm7 - Communication Diagnostic Software ver.7 .exe 2,470K Modbus RTU Example in Visual Basic 6.0 (.zip file) .zip 23K...

The transmitter's flow range/scale is determined by the flow (at design conditions) through the primary flow element, like an orifice plate or an averaging pitot tube. The primary flow element's vendor calculates the pressure drop at maximum flow rate and that's the value that used to range...

Assuming that you are referring to the controller status LED at the top; like most operational status LED's, its action is defined in the Installation and User Guide: The Installation and User Guide for HC900 Hybrid Controller, document #51-52-25-107 can be downloaded here...

Gerry, That is an excellent analysis and example. David

A two way isolator isolates the lines from each other. A 3 way isolator isolates the lines and the input power. I use a B&B Electronics 485OPDRI, but there are other makes and models http://www.bb-elec.com/product11.asp?sku=485OPDRI Be sure to take out any space in the URL above (forum...

This doesn't sound like a Modbus communication configuration issue. But it isn't clear what problem the cyclic voltage dip causes. I suspect a grounding problem through what is probably 2 wire RS-485 circuit. I'd put an RS-485 isolator module in the RS-485 circuit to see if the cyclic...

I use both Modscan32 and Simply Modbus. Either is entirely functional and suitable for establishing and proving serial or ethernet link communication to Modbus slaves. The first task in using either software package is to configure and establish the comm link, serial or ethernet, with...

The manual is here: http://www.documentation.emersonprocess.com/groups/public/documents/instruction_manuals/d102794x012.pdf (remove any space characters that the forum inserts into the URL) Plumbing double acting actuator on page 42; section 2-20. Wiring. Configuration needs actuator...

1) Device-Specific files for HART instruments are called DD's, "Device Descriptor" files, not dll's. 2) I find a file named "AutrolDD.zip" at http://www.autroltransmitters.com/aai/downloads.html under software & Manuals > Autrol DD Files (take out any space character that the forum...

1) >Those that can communicate are all on different power supply. A power supply acts as a low pass filter, which strips off the (relatively high frequency compared to the DC current) 1200 baud HART signal. The reason for the HART Foundation's minimum requirement of 230 ohm loop resistance...

Yeah, Omega has a line of temperature controllers with an integrated web server: http://www.omega.com/iSeries/iEmbed.htm (take out any space the forum inserts into the URL)