AB Communication,

[roxtech]

Hi, I am useing micrologix 1400 plc communicate with mypin weighing indicator. I read the actual value on indicator in plc with modbus address 40225. Now problem is on indicator weight value is 19kg standstill while in plc reading switch between two figer (19kg actual value and 4864). Anyone face this kind of problem. please help to find out problem in plc or problem in indicator.

 

[JeffKiper]

Just a wild guess have you tried byte swapping or word swapping? High to low.

 

[roxtech]

Yes, we swap byte. befor swap reading is ok but it wrong reading according to display display have high byte first.
regards,

 

[JeffKiper]

What format is the display using?

 

[Ken Roach]

If you use the "Swap Bytes" instruction, use different Source and Destination data table addresses.

Performing a SWPB on the same data table is just asking for confusion based on when the HMI happens to hit your database.

 

[roxtech]

Dear Jeffkiper,
its Hex formate total five byte read.
First two byte for point and other three byte for weight before desimal point.for example we read D8FF310000. its mean D8FF is point(after desimal point and 310000 is weight data before desimal point. According to indicator manufacturer. write data from right to left is 000031.FFD8H.
000031= 49
FFD8 = 99938.
So total Actual value is 49.99938Kg.
further when we Swap point word(byte to byte, we did not get same reading as display of indicator.

 

[Ken Roach]

If you can post your actual MicroLogix 1400 *.RSS program, or at least the relevant sections, that might help.

The value you are viewing switching back and forth between 19 (0x0013) and 4864 (0x1300) still suggests that you are using the Swap Bytes instruction incorrectly.

Do not use the Swap Bytes instruction with the same Source and Destination data table elements.

If you do so, the value you "see" in the RSLogix 500 data table monitor or ladder logic monitor will depend on the timing between the software update and the MicroLogix program scan.