Hello Looking for some thoughts on a project. I am trying to read a defender 3000 scale gross/net/tare data via RS232 into a productivity 1000 plc with the hopes of moving project to a 2000 plc.

the scale data is 18 characters long with two term characters 0d/0a.

I am most positive that the scale is sending out Gross, Net, and Tare weights as consecutive strings with the term characters between each. the scale is set to output data at 1(have also tried 3 and 5) second intervals

i had my scale set to continuous print and was able to use an ASCII IN to receive a good string with the scale gross weight. but that is all that I would get no NET or Tare weight data. I set my scale to interval and in the first shot my incoming ascii string would correctly show the gross, net, and tare weights in a repeating cycle very consistently one after the other.

this led me to make some logic to extract the 16th character from the incoming string which is either G, N, or T then do some string comparisons to store the first 11 characters of the string which is the actual weight data depending on what character is being read with one-shots and was able to store gross, net, and tare weights as individual strings.

then the way the data was coming in changed for some reason. now instead of the steady repeating cycle i saw at the beginning the incoming string is more static only showing mostly the gross weight and every now and again i see the NET and T characters show up but its totally random.

my problem is that my logic to read the weights works but somethings not right.

I put a 5lb weight on the scale, gross string: 5.00lb, Net String: 0.00lb, Tare String: 0.00lb

I press the tare button on the scale, gross 5.00lb, Net 0.00lb, Tare 5.00lb

I add 1lb to the scale, gross: 6.00lb, Net 1.00lb, Tare 5.00lb

So up to this point even though I do not see the incoming data fluctuating I think the PLC is reading the data correctly because its putting the right values into my strings using the comparison of the 16th character.

where things go wrong is when i try to clear the tare data at the scale head my string data gets messed up.

I press tare button on scale again, gross 6.00 lb Net 0.00 lb, Tare 6.00lb

I remove all weight from scale: gross 0.00 lb, Net -6.00lb, Tare 6.00lb

I press Tare on the scale, gross 0.00lb, Net 0.00 lb, Tare remains at 6.00lb

there is my problem, by logic the tare data should revert back to 0.00 lb as that is what is on the actual scale. I am assuming this would work just as if i was applying weight and implementing the tare. I tried some rising and falling one shots on the lines that store the weight data not sure what i was thinking or why I thought that would work but it did but only for a while then it went back to the same error so I'm thinking it was more of a timing issue and not anything I did with the logic.

sorry for the paragraphs but just trying to put as much info out there to see if anybody has run into anything similar or has been able to read gross,net,tare weights from an ohaus defender 3000. maybe its a timing issue that I am not seeing. I can upload my program if needed

Thank you in advance

Ric L.