Do you have any advise in using LabWindows V7 and Acromag's ESW-MBLIB C-libraries for developing MB TCP/IP drivers to communicate with Acromag's BusWorks or EtherStax I/O?

Try adding the keyword "struct" in front of the command/response buffers declaration for each Modbus command. That should help. See an example below for the Report Slave ID command/Response example. Notice the keyword "struct" has been added and shown in bold.

// ReportSlaveID command int ReportSlaveID(SOCKET sock, unsigned char* anRegValues) {struct ReportSlaveIDCmdMsg cmd; struct ReportSlaveIDRspMsg rsp}

I need a dual-input/single-output converter that accepts two 4-20mA PLC analog output signals and allows either signal to be selected as the converter output by a digital PLC output.

This is for a redundant PLC I/O application - if either PLC output fails the other output is selected as the 'duty' control signal to the control valve.

Automatic control/selection 1 pc., Model 892M-0500 Math Module with 2AO's and 1 AO.
This product can accept two 4-20mA inputs and provide one 4-20mA output. you could enter a simple "excel spreadsheet type equation" that automatically selects the higher of the two inputs. So, if one is lower or drops down to 0mA in case of failure, the other channel will kick in automatically. Example equation: Output=Max(A,B,4){with this equation, you'll clamp the lowest output of the 892M to 4mA}

We have six level transmitters with 4-20mA output signals that need to be displayed in a control room about 500 feet away. What is the best way to run these signals given that we only have Ethernet Cat5 copper or fiber optic cable available in the plant?

Acromag has a feature specifically engineered for Ethernet networks called i2o. This feature allows input remote I/O modules to talk directly to output modules. In the typical network, there is a Master and many Slaves where the Slaves cannot talk to each other, only to a Master. With i2o, no Master, no special software, and no dirvers are required, the i2o feature can also act like an extended signal conditioner or a wire saver. For this application, the Acromag 961EN-4006 with six current inputs can accept the 4-20mA signals. Connect this input module to the Ethernet cable near the level transmitters, then connnect an output module, 973EN-4006 with six current outputs each, to the existing Ethernet cable at the control room. The input module is configured via the built-in web pages to send a message to one or two IP Addresses per signal. Messages are sent periodically based upon a time you choose. The i2o feature allows you to transmit six signals over one cable.

Is it possible my network's firewall or Proxy Server is interfering with communication to my Ethernet I/O Modules?

Yes. Many industrial networks use a Proxy Server to create a firewall. With this configuration, the Proxy Server prevents the computer from communicating with the module. If using the Internet Explorer browser, to to the top tool bar and click: Tools / Options / Connections / LAN Settings. Then Uncheck the Proxy Server.

I will be configuring an Acromag Ethernet module from my PC before installing the module on our network. How can I set up my PC to be able to switch from the Internet to the module without changing TCP/IP settings each time?

If you PC is configured to connect to the internet or a corporate network, then you can temporarily change the TCP/IP configuration, via LAN Connection / Properties from the Control Panel. See the Acromag User Manual, "Connecting Acromag Series 900EN Ethernet Modules To Your PC." You will then not be able to connect to the internet or the corporate network.

If you need your PC to communicate with the Acromag module and also be able to go on the Internet or a corporate network, then you will need to install a second network interface card. The PC browser will know to communicate with the module when entering the module's default IP address into the browser's address field.

Why do I get a connection error after changing the IP address on the "Network Configuration" page?

Your module is now at a new address and the browser is still listening at the old address. You must enter the module's new address for the browser to find it again. Then go to your Internet Browser and select the following: Tools/Internet Options/Settings (on the General Property Page)/ and click on "Every Visit to the Page" with in the "Check for Newer Versions of Stored Pages" area. in many cases, this setting is defaulted to "automatic". You may need to reboot your computer and then try reconnecting with the module.

Why do I get a connection error after submitting a change on the "Network Configuration" page?

This is normal behavior. When making a network configuration change, the server in the module must be stopped and then re-started with the new configuration. Your computer may or may not sense this temporary "lost" connection and display a connection error page. If it does, hit the refresh button one or twice to get back to where you were.