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The error typically indicates that the PC serial port Modpoll is attempting to use is already in use by another application. Did you check Device Manager to see which COM port your USB/RS-xxx converter is installed on? Is it installed on COM8? Do you have a 2nd instance of Modpoll running in...

I can't help you with the Siemens master, but I can tell you a sad tale about the Honeywell UDC 2500. The Ethernet IP address can only be configured with Honeywell PIE software. There is no means to configure the IP address via the keyboard. The default IP address for the 2500 Ethernet card...

The signal conditioning module API 4402G does the math (A+B)/2; the average of 4-20mA signal A and 4-20mA signal B. https://api-usa.com/pdf/api/api4400g-4408g.pdf

There are general purpose isolators (4-20mA in; 4-20mA out) that are not rated for intrinsically safe application; they're just used for isolation. If that's what you call an 'isolator' then a general purpose isolator is different from an I/S rated isolated barrier.

I don't know the details of turbine combustion, but in general, I have to ask, 1) is the replacement technology rated for continuous duty? Some UV detectors will latch "ON" (fail un-safe) after continuous exposure to a flame. A mechanical shutter mechanism is used to block the UV and the...

Thanks for the update. Someone is likely to benefit from your experience in the future.

Any Modbus slave has some means to set the slave address locally on the slave itself. There are mechanical means, like DIP switches or rotary switches (0-9). Or a slave ID setting done through a pushbutton/display HMI menu. Or a setting done using a utility program and comm cable used to...

I agree. I, too, found it difficult to locate how to ask a question (start a thread) - In the red menu bar at the top of the screen, click on 'Forums' - Select 'General Discussion' - At the top of the General Discussion page there is a red, 'Post New Thread' button link to that page...

Modbus is not plug-and-play. Modbus is a project. Congratulations, you're the project engineer! This document covers an overview of implementing Modbus in the field. It assumes that the devices have commercial Modbus functionality. If you are writing your own Modbus code, you need a...

I normally stay out of DCS opinion polls, but it’s apparent to me that the availability of local support should be a major criterion. There is little public forum support for DCS’s like there is for PLC’s, so the ability to get support from an ’authorized’ source, whether that’s factory...

which language? link to manual with Modbus information?

In post #1 you state: >Also I set modbus slave simulator at another computer and tested. It was successful. I interpret that as Modpoll on PC #1, slave simulator on PC #2. In post #13, you state >I just connected primary PC and bluelog only. I didn't connect slave simulator on a secondary PC...

Honeywell's LX that runs the C300 processor lists the time functions shown below. I assume PKS has those as well.

maybe a sketch would help . . .

There are commercial products made to address the problem of RS-485 star networks, like the one below. https://www.icpdas-usa.com/documents/I-7514Udata.pdf

"Using what's readily available." Boy, does that cover a lot. I think I've seen 4-20mA wired with everything in Ace Hardware's electrical department (except lacquer coated motor/coil winding wire): Zip cord (typically used for US lamps), Romex, bell wire (solid, non-twisted pair), speaker...

Agree, it seems like overkill. The home-run-to-JB is the longer run, isn't it? I2R voltage drop for 20mA is pretty low for a typical JB-to-instrument run, so I doubt was the consideration. But who knows?

The manual on the web is a 30 page light-reading feel-good brochure. What's the link to the comm manual that covers Modbus/TCP functions?

I can't answer your question but you should know that a 4 byte CRC will not work with Modbus RTU. And Modbus TCP strips out the 2 byte CRC because TCP handles the error checking.

You connected a Modbus Slave simulator on a secondary PC and talked to it with Modpoll on the primary PC, correct? That eliminates the PC firewall issue - Modpoll is getting through the PC Firewall. Can you take the PC with Modpoll and connect it locally to the field device (or bring the...