S7 v5.6 4-20ma scaling issue
- Thread starter mass89
- Start date
You should meter mA first.
Then check if mA reading is same than raw value on plc.
If raw value isn't right, then check wiring and wago configuration.
FC105 is expecting 0 to 27648 raw values from card.
Best would be mA simulator, so that you can check easily if values are right or not.
4mA should be 0 on raw data.
Then check if mA reading is same than raw value on plc.
If raw value isn't right, then check wiring and wago configuration.
FC105 is expecting 0 to 27648 raw values from card.
Best would be mA simulator, so that you can check easily if values are right or not.
4mA should be 0 on raw data.
danw
Lifetime Supporting Member
can I ask what is going on here? I’m not a Siemens guy so I would think that a signed 15 bit 20mA value would be 32760 (or thereabouts) counts.
Do Siemens AI mA conversions always produce 27468 counts for 20mA (presumably for 4-20mA to eliminate 4mA offset?)?
As far as i know siemens always using 27648 yes, that is why i didnt think twice.
My wago is 12 bit res but producing word of 32760 which explains being approx 20% out, coincidentally approx 4ma worth
I was always under the impression a siemens ai at 4ma yield 5300 raw
My wago is 12 bit res but producing word of 32760 which explains being approx 20% out, coincidentally approx 4ma worth
I was always under the impression a siemens ai at 4ma yield 5300 raw
L D[AR2P#0.0]
Lifetime Supporting Member
Siemens scaling
L D[AR2P#0.0]
Lifetime Supporting Member
current inputs:
It won't make any difference if card have resolution 14 or 15 bits, raw data is for both cards from 0 to 27648 and same FC105 can used for scaling.
Depending of card input settings (0 or 4mA) raw data 0 is 0mA or 4mA. 20mA is allways 27648.
under 4 and over 20mA is also measurement and then raw data is showed under/over also.
PT100 cards have temperature *10 on raw data.
https://support.industry.siemens.co...f-analog-module/12345/?page=0&pageSize=10#top
https://support.industry.siemens.co...-transmitter-scaling/23788?page=0&pageSize=10
cardosocea
Member
I also remember that Wago had the possibility of choosing the Endianness of an IO block.
Somehow a top developer at a company I worked for thought that a range of 255 values on a high precision encoder was normal... he just didn't know what endianness. Mind that he was in an hierarchical top position, not that he was competent in any way.
Somehow a top developer at a company I worked for thought that a range of 255 values on a high precision encoder was normal... he just didn't know what endianness. Mind that he was in an hierarchical top position, not that he was competent in any way.
Dear all,
As I recall Wago AI (4-20mA) is a 12 bit resolution , bits 0,1,2 are status bits, The analog value is stored starting from bit 3 to bit 14 , For this reason the span is 32760 (you subtract the 7 which corresponds to 2^0 + 2^1 +2^2 )
I was in a training session where we successfully used FC105 to scale the input & we got an a curate result.
Regards
As I recall Wago AI (4-20mA) is a 12 bit resolution , bits 0,1,2 are status bits, The analog value is stored starting from bit 3 to bit 14 , For this reason the span is 32760 (you subtract the 7 which corresponds to 2^0 + 2^1 +2^2 )
I was in a training session where we successfully used FC105 to scale the input & we got an a curate result.
Regards
The Siemens scaling block will work correctly if the analog input is set to the actual mA range of the signal.
I.e. the signal is 4-20mA, then the analog input must also be set to 4-20mA.
The 20% error sounds as if the analog input is set to 0-20mA, or ±20mA.
Many analog input cards can be set to different signal ranges. This is done in the hardware configuration for each channel.
I like to use 0-20mA on the analog card even for 4-20mA signals. This because I can then freely program an alarm for low signal The integral low signal level alarm will trigger at 3.99A which gives nuissance alarms. Because of that I do not use FC105, but program my own scaling block.
I.e. the signal is 4-20mA, then the analog input must also be set to 4-20mA.
The 20% error sounds as if the analog input is set to 0-20mA, or ±20mA.
Many analog input cards can be set to different signal ranges. This is done in the hardware configuration for each channel.
I like to use 0-20mA on the analog card even for 4-20mA signals. This because I can then freely program an alarm for low signal The integral low signal level alarm will trigger at 3.99A which gives nuissance alarms. Because of that I do not use FC105, but program my own scaling block.
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