3/4/2012 8:55 AM  
Joined: 1/21/2012 Last visit: 5/13/2019 Posts: 56 Rating: (1) 
Hi Experts
The MM420 is showing the following act. Frequency values at certain set point: 4000 Hexa = 50 Hz 3000 Hexa = 37.5 Hz 2000 Hexa = 25 Hz 1500 Hexa = 16.4 Hz 1000 Hexa = 12.5 Hz 500 Hexa = 3.91 Hz My question is: According to the above values, the MM420 is notrunning in linear curve or linear scale (at 1500h & 500h), because the drive MM420 speed is get reference from analogue signal input (4 – 20 mA)to CPU314C2DP I think it suppose at:1500 h = 18.75 Hz instead of 16.4 Hz and also at500 h = 6.25 Hz instead of 3.91 Hz Please advise how to solve that problem … 
3/4/2012 1:15 PM  
Joined: 2/6/2009 Last visit: 1/16/2020 Posts: 917 Rating: (112) 
Hi, Which function blocks are you using?

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3/4/2012 3:18 PM  
Joined: 6/4/2008 Last visit: 1/18/2020 Posts: 1289 Rating: (294)

I think there is a calculation error in one of your scaling blocks. There is no set ratio between the two incorrect values (i.e. the error is not constant) I would suggest a little test, give a setpoint of 3500 Hex (14336 Dec) to your drive and if the drive setpoint is not 43.75 Hz, then there is definately a calculation error. Review your code. Regards, Graeme

3/5/2012 8:25 AM  
Joined: 1/21/2012 Last visit: 5/13/2019 Posts: 56 Rating: (1) 
Hi I'm using FB31 & FB32 ....???? 
3/5/2012 9:00 AM  
Joined: 1/21/2012 Last visit: 5/13/2019 Posts: 56 Rating: (1) 
Hi Graeme In fact I have executed the Siemens Exercise (please check the attached file) So the results which I got are according to that exercise ... Thank u 
3/10/2012 4:26 AM  
Joined: 2/6/2009 Last visit: 1/16/2020 Posts: 917 Rating: (112) 
Hi, Check the below links for the details about MM440 profibus communication, http://support.automation.siemens.com/WW/view/en/22813212=> Logic Examples It contains the sample projects for the communication between VFD and PLC with the calculation.

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3/10/2012 7:58 AM  
Joined: 5/28/2008 Last visit: 1/26/2020 Posts: 4158 Rating: (776)

In fact it is already run in linear scale. linearity should is not between actual speed and set point in hexa. but it should happen between actual speed and set point in dec. To sent a set point between 0  100% of full scale ( NB. 100% here is equal to P2000 of MM4 parameters if and only if it is less than or equal to maximum frequency). for example. if max. frequency is 50Hz. P2000 = 50 0  100% = 0  50Hz can be achieved by sending setpoint values between 0  4000Hex.
From above table, if you draw a curve between value in DEC & Hz, it will be a linear curve.
No. Values of 16.4 & 3.91 is correct for 1500h & 500h. I hope it is clear for you now from the above explanation and my above table. And Note that I have added an entry in the table (2CD4) hex, to remind you that you should first convert hex. numbers into dec. numbers and then you will find the curve is linear.


Ayman Elotaify 

This contribution was helpful to1 thankful Users 
3/10/2012 7:41 PM  
Joined: 10/10/2010 Last visit: 12/25/2019 Posts: 296 Rating: (13) 
thank you 
3/12/2012 9:03 AM  
Joined: 1/21/2012 Last visit: 5/13/2019 Posts: 56 Rating: (1) 
Hello Ayman Thank u for your valuable reply…. For scaling between / 0.0 – 100.0 % (Real) & 0  16384 (DEC) / Is there any converting function/instruction in order to convert from DEC format to Hexa format

3/12/2012 5:36 PM  
Joined: 5/28/2008 Last visit: 1/26/2020 Posts: 4158 Rating: (776)

[quote user="Dhiyia"] Hello Ayman Thank u for your valuable reply…. For scaling between / 0.0 – 100.0 % (Real) & 0  16384 (DEC) / Is there any converting function/instruction in order to convert from DEC format to Hexa format

Ayman Elotaify 

This contribution was helpful to1 thankful Users 
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