Search results

If you are using Modbus/tcp over cellular, keep in mind that there will be a lot of networking overhead traffic that deals with keeping a tcp socket open (eg ack's, nak's, etc.) And all of that traffic will place your cellular modem into transmit mode and therefore run down your battery...

Curt, You mentioned patents... I'm not aware of any patents that pertain to EtherNet/IP. Do you know specifically of any patents held by ODVA or Rockwell that cover EtherNet/IP?

Michael, The EtherMeter, which my company manufactures, might be a good fit for your application. It works with most off-the-shelf water meters and each unit can accept one or two meter inputs -- absolute encoder readings (revenue-grade accuracy) and/or pulse inputs. It can natively...

Keep in mind that with a proper positioner, motorized valves can be used to throttle flow, as well. Example valves include the Jamesbury Hi-Performance Butterfly Valve, and the Fisher Control Disk. Example positioners?... There are many that accept a 4-20mA position signal. EIM is a...

How about a PLC with two serial ports? -- the first configured as a modbus/rtu master over RS-485 (multidrop), and the other port as a modbus/rtu slave? I can think of many brands that could do this.

Rob, My company manufactures a meter interface device (the EtherMeter) that converts flow and totalization from many gas meters into Modbus and Rockwell comm protocols. For your Quantum PLC, you can get the readings using Modbus/TCP; and if you ever need to link the meter with an Allen...

Good info, Ronald. I also use butterfly valves in many control valve applications have had much success. And thanks for pointing out the Fisher Control Disk. I just read over their data sheets, and the product looks intriguing.

In these types of applications (protocol bridging), I always have to put in a plug for the Digi One IAP. I've used them on many occasions, and they work very well.

Fabian, My company manufactures a meter gateway ("EtherMeter") that can count (totalize) pulses from a flow meter and make the total (and flow rate) available in DF1, EtherNet/IP, and Modbus protocols. It will work with the E-H pulse output meter, as well as most "encoder-type" flow meters...

What make/model electromagnetic flow meter are you using?

For water applications, I usually place the control valve downstream of the flowmeter, because in that location, the valve will not be able to disturb the flow profile before the water hits the meter.

Yes. As long as the slave will support multiple simultaneous sockets (which it should).

Tom, For EtherNet/IP protocol communications, the C*Logix uses TCP Port 44818 and also UDP Port 2222 (maybe TCP Port 2222, also?). Forwarding those ports thru the router may help.

If the flow rate is represented as a floating point number, then you will be reading 32 bits of data, which spans two Modbus registers. When your polling program (Modbus master) puts together the two 16 bit registers into one 32 bit register, you need to make sure that the bit order is the...

If you want to measure the flow/totalization of a liquid/gas combo, and you want to look at the volume of liquid only (basically ignoring the gas content), then you'll probably want to use a "mass flow meter". There are many brands available, but I unfortunately don't have experience using...

Big Endian (Most significant data sent first).

I would install a very inexpensive PLC at the remote motor site and have it read an auxiliary contact from the motor starter. The auxiliary contact would be set up as an input to a discrete input channel on the PLC. Set up the PLC as a Modbus slave (if your plant control system can speak...

Ville, IMO, Bob Peterson has the best solution (and it's one of the simplest approaches, too). But I would probably tweak his approach... Because the only problem with his solution is that 1/2 hour of wind due north at 50 mph followed by 1/2 hour of wind due south at 50 mph would yield...

hutber, It would be great if the *logix PLC's spoke modbus/tcp, but unfortunately they don't. (The C*logix can, but only with an add-on card from Prosoft). Alternatively, you could also add a DOIAP to your network to translate between EtherNet/IP (logix) to Modbus/TCP (twido). I've used...

Roger, Within the RsLogix programming environment, you can view the error code in realtime for each of your message instructions. Double-click on the message instruction in RsLogix and watch for the error code to be displayed during execution. I've used the error-code to successfully...