convert real to word

Hi,

I have small problem , I have ABB AC 900F and I want to send the real value (for ex. PIT 0-6 Mpa) by mod slave to another DCS

the mod slave accept only word value and no convert from real to word directly only (int,dint and STR) since the mention type didn't send the point value (for ex. The pressure arrived to 2.7 ) The INT Shown >> 3 , DINT >> 3 and STR >> 0

I want your advice how can change the real to word without loss the point

Best regards

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ahmedfalah Rank: 4309

Asked 3 years ago

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It is not possible to keep the point value in word's. A basic attribute of word ist to have no point. Word also have value range from only 0 to 65535.

I would also avoid the string convertation, since it use more memory and calculaton power than other convertations.

I suggest to scale the value before converting to word, and use the detour over uint.

Value-->*10000-->TO_UI-->TO_WO---(Modbus)--->Convert_Real-->/100
00---->Value

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by ahmedfalah Rank: 4309 on 8/9/2016 10:45:56 PM | Like (0) | Report

Thank you sir,

I made this solution also but the team in FOXBORO side didn't accept to use any function block because their memory almost full,

I want to ask is there any mod slave function block can send the data as real ,I can buy it from ABB

Best regards

by Ordoban Rank: 30 on 8/9/2016 11:09:23 PM | Like (0) | Report

So take a look to the Real-->Mant./Exp.(RTOME) function block. It can be found on Modbus Master.

by ahmedfalah Rank: 4309 on 8/9/2016 11:18:45 PM | Like (0) | Report

not useful (FOXBORO side didn't accept to use any function block their)

by Ordoban Rank: 30 on 8/10/2016 12:43:21 AM | Like (0) | Report

Strange. You should ask the FOXBORO side what kind of data they would accept. Modbus can transfer binary (coil) or word (register) values only. Everything else must be split or convert before. Maybe the FOXBORO PLC can "receive" real by using 2x word internally.
Maybe you can mul the value by 1000 and offer this as kPa.

by JuergenV Rank: 74 on 8/10/2016 6:50:12 AM | Like (0) | Report

Does the FOXBORO support Half (16bit) floating point (IEEE 754-2008)? It is possible to create a user function block that converts from REAL to a WORD respresenting a Half precision number using TO_DW or RTOME to get the parts or bits of the REAL, and to construct a word that looks like a Half precision number from it using PBOWO (Pack Bool to Word).

by ahmedfalah Rank: 4309 on 8/10/2016 9:12:56 AM | Like (0) | Report

guyes
thank you for your support , the problem finally solved by convert the real to DWORD then from DWORD1 to DWORD0 (FB) and connect the both end of FB to the MOD SLAVE

thank you again and best regards

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Ordoban Rank: 30

Answered 3 years ago

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Hi,

check this thread

http://www402.abbext.com/REAL-IEEE754-32-bit-floating-point-q526962.aspx

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Govindaraj AKS expert

Rank: 10

Answered 3 years ago

Hi,

you need a two step process on both ends:

Convert the REAL to a DWORD with TO_DW, then split it into two WORDs with UPDWWO.

Now transfer the two WORDs.

On the other side: PWODW, then TO_RE. Don't know how this works in other DCS ...

Make sure the two WORDs are from the same REAL after transfer via MODBUS.

Best regards

Jürgen

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by ahmedfalah Rank: 4309 on 8/9/2016 9:23:29 PM | Like (0) | Report

dear JuergenV

the other DCS is FOXBORO DCS and the memory load their arrived to 78% they don't want to put any function block their because it will make a load to them since I have 72 analog signal to be transfer.

do you have another solution for this issue

thank you and best regards

by Ordoban Rank: 30 on 8/9/2016 10:59:19 PM | Like (1) | Report

dear JuergenV
TO_DW also chops away the point value. Did you had the Real-->Mant./Exp.(RTOME) convert in mind? This funtion block is the proposed way to transfer real values over modbus, but i would not suggest to use this - i have bad experiences using this block.

by JuergenV Rank: 74 on 8/10/2016 1:14:29 AM | Like (0) | Report

I hope the German documentation is correct. It says: No conversion, the TO_DW returns the bit pattern of the real.
RTOME cannot represent all values, could be an option too.
The best solution depends on what can be done to the value on the FOXBORO side. Maybe using the WORD as a fixed point float would be the best here. E.g. multiply by 10, then cut the point to get one digit after the point, but range would be limited to 0..6553.5

by Ordoban Rank: 30 on 8/10/2016 1:59:32 AM | Like (0) | Report

You are right! I just tried it out. So the TO_DW convert work different to all other real to bin operations. In this case TO_DW would be the best solution, if the "FOXBORO-Side" can do an internal merge to real (like many other DCS can).

by ahmedfalah Rank: 4309 on 8/10/2016 9:13:52 AM | Like (0) | Report

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JuergenV Rank: 74

Answered 3 years ago

Hello,

As ordoban replied use default convertor blocks or RTOME FB, add those block at ABB side and you can convert whatever datatype into words and can send it via modbus to thidparty device, Now it depends on thirdparty device in which data type format it recieves...

Check image here there are two possible ways you can send real data over modbus from AC900F, may be need to swap a bytes depending on receiving side...

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Sumit Gargav AKS expert

Rank: 3

Answered 3 years ago

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convert real to word

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