Abby Posted June 28 Report Share Posted June 28 Hello, I wanted to see anyone opinions' on the wiring of my Dissolved Oxygen Sensor to Unitronics UAC-CX-01RS4. This is my first time working with Modbus, So far in testing I have only received a 0 for my read values for DO mg/l, DO Oxygen sat %, DO ppm, and DO Temp Celsius. And for the Status I have received a -11 for all 4. This is how I interpreted the wires are connected from: White wire RS485 (command) to D- on the UAC-CX-01RS4. Brown Wire RS485 (Data) to D+ on the UAC-CX-01RS4. Pink wire to 12VDC. Blue wire to Signal Ground (SG) on UAC-CX-01RS4. I am unsure if the Functional ground needs to be connected to anything from the Unitronics UAC-CX-01RS4. Right now its left unused, but at this point I feel like it should be going somewhere. Thank you for any help. Link to comment Share on other sites More sharing options...
MVP 2023 kratmel Posted June 28 MVP 2023 Report Share Posted June 28 Please post Sensor model # or pdf manual. Some sensor must be configured by OEM software before connect to Modbus network. I see (data) (command) pinout - it is not Modbus standard pinout. Maybe sensor is not Modbus by default (some configuration bit must be set for Modbus enable). 1 Link to comment Share on other sites More sharing options...
MVP 2014 Simon Posted June 29 MVP 2014 Report Share Posted June 29 Functional ground is not likely to be an issue for basic testing. It would normally connect to the physical ground, like the metal enclosure or racking, etc. Baud rate and other serial parameters need to match. I see you have set 9600 baud. Was that from the sensor datasheet? It is also common with RS485 that the data wires aren't labelled consistently between different manufacturers. For example A/B or +/- and so on. If you are sure everything else is correct, try swapping the two data wires. Also with termination, whilst everyone says to add it, on very short networks I find it is often necessary to remove termination. So if you are just testing with a short cable between the PLC and the sensor, try with and without termination. I hope this helps. Simon Link to comment Share on other sites More sharing options...
MVP 2023 Joe Tauser Posted June 30 MVP 2023 Report Share Posted June 30 Your poll time is too fast for RTU and is shorter than your response time. You're filling up your buffer. For testing I'd set your poll time to 5 sec each until you get it functional. Then you can speed it up and see where it starts choking. Joe T. Link to comment Share on other sites More sharing options...
MVP 2023 Ausman Posted June 30 MVP 2023 Report Share Posted June 30 And like is mentioned all over the forum, the best method for working with a new modbus device is to learn about it using your PC. Any number of the free modbus utilities found on the web will suffice. The whole point is that it is far easier to find what works and what doesn't, by using the PC. Once you've got it all figured out, it is vastly easier to then shift all those known parameters to the PLC. And a question I don't know the answer to...does Unistream do the 1 digit difference in register numbers like Vision does? Perhaps this is your issue in the first place...? cheers, Aus Link to comment Share on other sites More sharing options...
Abby Posted July 1 Author Report Share Posted July 1 The Model number is a Sensorex ODO8000. Sensorex ODO8000 manual Link to comment Share on other sites More sharing options...
MVP 2023 Ausman Posted July 1 MVP 2023 Report Share Posted July 1 I had a quick look at the manual and I'll leave the connection issue to Kratmel who is more used to quirky connections. I'd need one of these on the bench to be sure of things. Looking at some of the registers in the sensor, I'd be very careful with your testing, so that you don't accidentally upset some crucial setting which might be done in registers, both listed and unlisted! I again suggest doing it all on the PC first. I use Modbus Poll and a link below..... but this is the trial that only runs for 10 minutes. Some other freebies are fully functional. https://www.modbustools.com/download.html Link to comment Share on other sites More sharing options...
pascal Posted July 22 Report Share Posted July 22 On 7/1/2024 at 1:00 AM, Ausman said: And like is mentioned all over the forum, the best method for working with a new modbus device is to learn about it using your PC. Any number of the free modbus utilities found on the web will suffice. The whole point is that it is far easier to find what works and what doesn't, by using the PC. Once you've got it all figured out, it is vastly easier to then shift all those known parameters to the PLC. And a question I don't know the answer to...does Unistream do the 1 digit difference in register numbers like Vision does? Perhaps this is your issue in the first place...? cheers, Aus The 1 digit difference.... nice said Ausman ! I don't think this is a Unitronics issue (Unilogic or Visilogic). This depends only on the manufacturer of the modbus device ! I've had devices I could use the mentioned adress of the manual and others, where I must substract 1 for correct reading of the data. Even whit the advanced modbus instructions, where you make your own modbustelegram's, it is trial and error.... I use powerhud modbus tester tool on my PC -> www.powerhud.com (also free and no timeout...) with more features (big or little endian,...) Link to comment Share on other sites More sharing options...
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