We are using codesys as a development tool for GUI application. We developed a function that displays real data type value to user. We are facing problem of displaying / processing the real values after certain limit.
For e.g refer the attached project.
In the attached project we are adding two real values 33554442.5 + 2.5 and the result was 33554448.00, So could you please help us to get correct value 33554445.00.
Regards
Rajesh G
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Anonymous
-
2010-03-25
Originally created by: Mikhail Shvetsov
use LREAL type, i've checked up it works.
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Anonymous
-
2010-03-26
Originally created by: Mikhail Shvetsov
Real type has 32 bits, but mantissa of real type has only 23 bits. It’s a reason of limits data accuracy about 7 decimal numbers. Your values of variables acquire 8 numbers, and last number is wrong.
LREAL type has twice more bits of mantissa then REAL type.
If you don’t have LREAL you should write special function (IMHO) which would be able to work with “compound” data.
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Could you please provide more information on IMHO function. How to implement?
Regards
Rajesh G
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Anonymous
-
2010-03-26
Originally created by: Mikhail Shvetsov
IMHO - In My Humble Opinion. You misunderstood me. It’s my fault, sorry.
Ok, do you have DINT ( UDINT ) type? This type has 32 bits and you could use 10 numbers. You can convert REAL type into UDINT (or DINT if you need “-“) by multiplying to integer. After that it becomes possible to operate without missing accuracy.
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We are using codesys as a development tool for GUI application. We developed a function that displays real data type value to user. We are facing problem of displaying / processing the real values after certain limit.
For e.g refer the attached project.
In the attached project we are adding two real values 33554442.5 + 2.5 and the result was 33554448.00, So could you please help us to get correct value 33554445.00.
Regards
Rajesh G
Originally created by: Mikhail Shvetsov
use LREAL type, i've checked up it works.
Our target will not support LREAL.
Regards
Rajesh G
Originally created by: Mikhail Shvetsov
Real type has 32 bits, but mantissa of real type has only 23 bits. It’s a reason of limits data accuracy about 7 decimal numbers. Your values of variables acquire 8 numbers, and last number is wrong.
LREAL type has twice more bits of mantissa then REAL type.
If you don’t have LREAL you should write special function (IMHO) which would be able to work with “compound” data.
Could you please provide more information on IMHO function. How to implement?
Regards
Rajesh G
Originally created by: Mikhail Shvetsov
IMHO - In My Humble Opinion. You misunderstood me. It’s my fault, sorry.
Ok, do you have DINT ( UDINT ) type? This type has 32 bits and you could use 10 numbers. You can convert REAL type into UDINT (or DINT if you need “-“) by multiplying to integer. After that it becomes possible to operate without missing accuracy.