You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old February 27th, 2020, 06:44 PM   #1
Meyers Mills
Member
Ghana

Meyers Mills is offline
 
Join Date: Dec 2019
Location: Accra
Posts: 21
Scaling

Hello
I need help in understanding the Concept of scaling analogue outputs from flow meter, Thermocouple or pressure transmitters into a PLC. Precision is very important in this arena and errors could costly. What is the best way to scale analog values accurately ?I use Do More Designer software but ,Other brands like Siemens can be used for illustration
Secondly, I want the link I can use to download RSLOGIX Plc simulation software, some links on the internet don't work.

Thanks
  Reply With Quote
Old February 28th, 2020, 05:04 AM   #2
ivo.maenen
Member
Belgium

ivo.maenen is offline
 
ivo.maenen's Avatar
 
Join Date: Nov 2003
Posts: 663
standard signals can be eg



0-10 V, -10 - 10V

0-20 mA of 4-20 mA




this will be converted to a value between



0- 32767 (0-10V)
-32767 - +32767


for signal 'temperature-resistance' this will be the





the temperature * 10
eg -250° => -2500






You'll need to scale this to your proces value


eg


sensor / PLC-input

0 bar = 0 V = 0

20 bar = 10V = 32767



so


PLC-value-calculated



32767 => 20 bar

1 => 20 bar/32767


if not the value '1' but '222' then



222 => 222 * (20*32767) bar = 1,368 bar





The calculation basically should be like this equation:



y = a*x
__________________
Assumptio mater errorum est.
  Reply With Quote
Old February 28th, 2020, 05:21 AM   #3
chopin
Member
United Kingdom

chopin is offline
 
Join Date: May 2012
Location: Milton Keynes
Posts: 186
Try rockwell automation website.

You will need to create an account with commercial email account then you may have access to downloads although I am not 100% sure.

It may as well be that without paying you will not be able to download even trial version.

You have to try.
  Reply With Quote
Old February 28th, 2020, 08:37 AM   #4
gclshortt
Member
Canada

gclshortt is offline
 
gclshortt's Avatar
 
Join Date: Dec 2014
Location: Ontario
Posts: 3,053
https://accautomation.ca/brx-plc-ana...configuration/

The above link will show the BRX (Do-More Designer) scaling that is done with the analog card.

Regards,
__________________
Garry
https://www.accautomation.ca
Connect with us on Facebook: facebook.com/accautomation/
  Reply With Quote
Old February 28th, 2020, 02:06 PM   #5
NetNathan
Lifetime Supporting Member
United States

NetNathan is offline
 
Join Date: Nov 2011
Location: Corona, CA
Posts: 1,669
You could use a scale block to solve...
What PLC?
__________________
****Control Freak****
Net is where I be and Nathan is me.
  Reply With Quote
Old February 28th, 2020, 02:35 PM   #6
Rson
Member
United States

Rson is offline
 
Join Date: Jun 2017
Location: Michigan
Posts: 300
y = mx+b
  Reply With Quote
Old February 28th, 2020, 02:55 PM   #7
Tom Jenkins
Lifetime Supporting Member
United States

Tom Jenkins is offline
 
Tom Jenkins's Avatar
 
Join Date: Apr 2002
Location: Milwaukee, WI
Posts: 6,032
This thread may help: http://www.plctalk.net/qanda/showthread.php?t=61912

Note that you can't do much to improve the basic accuracy of the PLC analog input card A/D conversion. If the floating-point math is correct or you use a standard function like SCP you get what you get. Note, however, that a 12-bit input provides resolution to one part in 4095, which is +/- 0.02%. This will greatly exceed the accuracy of almost any transmitter.
  Reply With Quote
Old February 29th, 2020, 12:30 PM   #8
VAN
Member
United States

VAN is offline
 
Join Date: Apr 2012
Location: Wa
Posts: 322
https://www.divize.com/techinfo/4-20ma-calculator.html

This is for a straight line... if you have a curve sometimes excel can give a decent formula that you can cpt the output from the input. Curve fitting is probably not what you are asking for.
  Reply With Quote
Old March 1st, 2020, 05:58 AM   #9
drbitboy
Lifetime Supporting Member
United States

drbitboy is offline
 
drbitboy's Avatar
 
Join Date: Dec 2019
Location: Rochester, NY
Posts: 356
Thumbs up RSLOGIX Plc simulation software

Quote:
...Secondly, I want the link I can use to download RSLOGIX Plc simulation software, some links on the internet don't work.
To get the RSLogix Micro Starter Lite, RSLinx Classic, and RSLogix Emulate500, I think this video https://www.youtube.com/watch?v=tJLEx44HacY is still current. However, when you get to 1m40s (one minute, forty seconds) in that video, you may need to click the plus sign (+) to the left of [1763-Lxxx (series B)] to see what is shown in the video; see the image below.


You will also need to have or create an login for Rockwell Automation to do the download; I was able to do so with an @gmail.com email address.
Attached Images
File Type: png xxx.png (39.8 KB, 113 views)
  Reply With Quote
Old March 1st, 2020, 07:26 PM   #10
drbitboy
Lifetime Supporting Member
United States

drbitboy is offline
 
drbitboy's Avatar
 
Join Date: Dec 2019
Location: Rochester, NY
Posts: 356
Wink The essence of engineering is multiplying by unity

To answer the scaling question, you need to know the Secret of Engineering: the act of [multiplying by one] describes 80% or more of all engineering tasks; the rest is determining the value of one for each task.


For example, say someone tells you that it takes them 4.3 hours to drive from Accra to Kumasi, and they want to know how many minutes that is. You know that one hour is sixty minutes, and you write that down as an equation:

Code:
  1 hour = 60 minutes
Then you divide both sides of the equation by one hour:

Code:
 1 hour     60 minute
 ------  =  ---------
 1 hour     1 hour
(one hour) divided by (one hour) is 1, as is anything divided by itself, so the equation simplifies to

Code:
 1 = (60/1) (minute/hour)
 1 = 60 minute/hour
The multiplicative identity property states that any time you multiply a number by 1, the result, or product, is that original number. So you multiply your original 1.5 hours by 1, and then replace the 1 with [60 minutes/hour], which is the same as 1 as shown above:

Code:
 4.3 hours x   1             =  <<<---Multiplying by 1!

 
 4.3 hour      (60 minutes)     
           x   (----------)  =  <<<---Also multiplying by 1!
               (  hour    )
 
 
 4.3 x 60 hour minute
 --------------------
            hour
The [hour] units in the numerator and denominator cancel:

Code:
(4.3 x 60) minute = 258 minutes
So 4.3hours is the same as 258 minutes, and we know that because we multiplied the former by one (in the form or 60 minute/hour) to get the latter, and the multiplicative identity property tells us that the product of a number and one is same as the original number.


In the same way, the task of scaling physical values in a digital can usually be reduced to the task of multiplying by 1. There may be some second-order steps required, such as if the two scales do not meet at zero, or if the sensor output is non-linear with respect to the physical property measured, but that all falls in the 20% of the task of determining the value of one.


For example, consider a flowmeter that you have calibrated in your process: at a flowrate of 0 m3/h it sends a signal of 0V to your PLC analog input; at a flowrate of 123 m3/h it sends a signal of 6V. Using the same approach, we can say that 6V is the same as 123 m3/h:

Code:
 6V = 123m3/h
 6V/6V = 123m3/h / 6V
  1 = 20.5 (m3/h)/V   <<<---The “value” of 1
Furthermore, the 0-10V signal into the analog input of the PLC is converted to a numeric value, which I will call a Data Number, or DN. For this example: at 0V, the DN is 0; at 10V the DN is 16383; so 16383DN is the same as 10V:

Code:
 16383DN = 10V
 16383DN/16383DN = 10V/16383DN
 1 = 0.000610389 V/DN    <<< Another “value” of 1
Note that we can combine these values for 1 by multiplication (or division), and the value will still represent 1:

Code:
 1 x 1 =  [20.5 (m3/h)/V] x [0.000610389 V/DN] =  
 [20.5 x 0.000610389] [(m3/h)/V V/DN] =
  0.012512971  (m3/h) / DN     <<< Yet a third “value” of 1
And for a sanity check, the DN values for 6V (123 m3/h) would be 60% of 16383DN which would be a little less than 10kDN, and 10kDN x 0.0125... (m3/h)/DN would be about 123m3/h, as expected.


That is the essential approach to take for scaling, and that is the essence of engineering in general.


One case not covered abvoe is when the two related representations (e.g. Volts and m3/h above) are not both zero at the same point. One example would be a typical current-based analog inputs that scale 4-20ma to 0-16383DN or a thermocouple channel where zero DN corresponds to some non-zero temperature (e.g. one type L thermocouple input module specifies a temperature range of 300 to 1800°C corresponds to a range of -76.5mV to +76.5mV and a range of -32768DN to +32767DN). Ignoring the non-linearity of thermocouple systems for the purpose of this illustration, the solution is to use the general form of the scaling equation:

Code:
 (CalibrationTemperature – 300)°C      (MeasuredTemperature - 300)°C
 --------------------------------  =   -----------------------------
    (CalibrationDN - (-32768))DN          (MeasuredDN - (-32768))DN
Where all values except MeasuredTemperature are known. This post has been using this form implicitly all along, but the subtrahends (300 and -32768 in this case) were both zero, which reduces the scaling equation to this:

Code:
 FullRangeValue(engineering units)     MeasuredValue(engineering units)
 ---------------------------------  =  --------------------------------
      FullRangeDN(DN units)                 MeasuredDN(DN units
Solving for the measured value from that general form of the scaling equation yields this:

Code:
                 (CalVal – CalLowVal)
 MeasuredVal  =  -------------------- x (MeasuredDN – CalLowDN) + CalLowVal
                   (CalDN – CalLowDN)
Which is more commonly expressed as

Code:
  y = mx + b
And that is exactly what Rson gave as the answer to the OP: [m] is a “value” of 1; [b] is an offset.

Last edited by drbitboy; March 1st, 2020 at 07:31 PM. Reason: fix typo
  Reply With Quote
Old March 1st, 2020, 09:18 PM   #11
dcam
Lifetime Supporting Member
United States

dcam is offline
 
dcam's Avatar
 
Join Date: Apr 2012
Location: Merced Ca
Posts: 137
From the land of AB this is what analog inputs look like. Recent Chill water program I did.

4mA = 0% of a spanned instrument = raw value of 3277
20mA = 100% of spanned instrument= raw value of 16383

The CHILL_TANK_LEVEL raw value was changed for a quick adjustment, I need to go back and respan press transducer to correct.

If MicroLogix then Scale with Parameters instruction.
Attached Images
File Type: png 5000SCL.PNG (23.6 KB, 90 views)
  Reply With Quote
Old March 1st, 2020, 11:22 PM   #12
BobB
Lifetime Supporting Member
Australia

BobB is offline
 
BobB's Avatar
 
Join Date: Jun 2002
Location: Sydney
Posts: 4,365
Wink

From the world of Omron. Pics show the outside of the block, inside of the block (ST) and several shots of this showing inputs, outputs and internals. Output by REAL, integer and BCD - integer and BCD lose the decimal points. Works really well - I normally use REAL but sometimes integer if I do not want tyhe resolution.
Attached Images
File Type: jpg Scaling 1.jpg (33.6 KB, 17 views)
File Type: jpg caling 2.JPG (57.5 KB, 10 views)
File Type: jpg Scaling 3.JPG (61.8 KB, 11 views)
File Type: jpg Scaling 4.JPG (59.1 KB, 10 views)
__________________
The Old Pfhaart

  Reply With Quote
Old March 2nd, 2020, 01:53 PM   #13
PLCnovice61
Member
Australia

PLCnovice61 is offline
 
Join Date: Apr 2015
Location: home
Posts: 182
Hi dcam, is that a typo/wire error or is there a reason you have 2 different inputs on H20_IN_PSI, InRawMin/InEuMax?
I imagine it is just very small gap that is not being displayed between the wires, but it may be confusing for some (me at least initially).
Kevin

Last edited by PLCnovice61; March 2nd, 2020 at 01:58 PM.
  Reply With Quote
Old March 2nd, 2020, 08:37 PM   #14
dcam
Lifetime Supporting Member
United States

dcam is offline
 
dcam's Avatar
 
Join Date: Apr 2012
Location: Merced Ca
Posts: 137
Unsure what you mean.

Not sure what you mean? There is only one input the H2O psi...just like the Glycol psi. Maybe im not seeing what you are pointing out. This is a pict of working logic. heres a pict of my PV. Please let me know in more detail what you are asking.
Attached Images
File Type: png TableChill.PNG (64.7 KB, 51 views)
  Reply With Quote
Old March 2nd, 2020, 08:56 PM   #15
Ron Beaufort
Lifetime Supporting Member
United States

Ron Beaufort is offline
 
Ron Beaufort's Avatar
 
Join Date: Jul 2002
Location: Charleston, SC
Posts: 5,581
just a guess - but I've got a hunch that he's talking about this area where the two lines overlap ... that's just something that happens with the FBD display from time to time ... dragging the signal references around a little bit usually clears it up ...

note that the code won't be confused by the "overlapped" display ...
.
Attached Images
File Type: png overlap.PNG (6.6 KB, 52 views)
__________________

2-B ?
Best regards, ----+----] [----+------------( )----
Ron | |
PLC Training Boot Camp - Retired | 2-B |
+----]/[----+

I once was lost, but now am found, was blind, but now I see.


Last edited by Ron Beaufort; March 2nd, 2020 at 08:59 PM.
  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
PLC5 Scaling Question jrowe4 LIVE PLC Questions And Answers 3 July 18th, 2014 06:27 PM
PT100 Scaling in RSlogix 5000 InstrumentationUK LIVE PLC Questions And Answers 6 February 5th, 2014 08:55 AM
ControlLogix and Devicenet Christoph LIVE PLC Questions And Answers 16 October 5th, 2013 10:17 AM
how to determine low,high,and mean scaling for Omron? kartika LIVE PLC Questions And Answers 5 August 2nd, 2011 02:20 AM
ControlLogix PID Scaling - Help! kdcui LIVE PLC Questions And Answers 4 May 10th, 2011 06:09 PM


All times are GMT -5. The time now is 08:50 PM.


.