Scale Value

baler

Member
B
Join Date
Nov 2005
Location
West New York, NJ.
Posts
29
Hi! I'm trying to obtain a scaled value for a distance of 1090 units (10nths of 1")read by a distance laser in the range of 4-20ma. I want to use percentage range. How do I go about it?
I'll appreciate any help. Thank you.
 
More info would help us help you.

What processor are you using?
If the analog signal is connected to an analog card , what is the catalog number of the card? And if you have configured the card, how have you set it up?

Post the program file if you can.
 
Hi Mickey, thank you very much for your interest.
I don't have a program yet, but I'm going to use a 1769-L32E controller and 1769- MODULE ANALOG INPUT.
I'm really interested in what numbers I should use when I apply the formula for scale value. Specifically to obtain the rate if it is expresed in 0-100%.
In other words, if I use a compute instuction,what would be the expreson factors? Thank tou again for your time.
 
You configured it in the module itself providing you have correct version of RS5000. You select the type of analog (0-10, 0-20, 4-20 in your case. You then select "Percent Range" in the "Data Format". I selected a 1769-IF8 to test this. There are other ways to do this. Do a search here on scaling if you want more info.
 
Thank you Mark.
Input type: 4-20ma.
Input data format: Percentage range
Max. scale value: 1090
Min.scale value: 0
Compute instruction: expression= raw data from analog input card * or / by what factor? Can you tell me?
 
Hello,

Well there is some confusing, mixing of terms, at least for me.

You say percent range, then you say 4-20 or 0 - 1090.

What I provided was the percent of full scale (PFS).

PFS = (100 / (input range high - input range low)) * (input value - input range low)

PFS = (100 / (1090 - 0)) * (input value - 0)

or

PFS = (100 / 1090) * input value

It seems you just want scaling. Which could be:

value = (raw in - IR Low) * ((EU high - EU low) / (IR high - IR low)) + EU low

value = (analog card in - 4) * ((1090 - 0) / (20 - 4)) + 0

or

value = (analog card in - 4) * ((1090 / (20 - 4)))

or

value = (analog card in - 4) * (1090 / 16)

or

value = (analog card in - 4) * 68.125

Excel is a wonderful tool for testing. Just looking you can see the mid-point for the 0 - 1090 is 545 and the mid-point for 4 - 20 is 16.

So, enter the formula and 16 = 50% = 545. If you get a different value the formula is broken.

Good luck,


Mark
http://www.peakhmi.com
 
Last edited:
Scaling always throws me too, I appreciate the info. :)
I'll play with it in Excel, per your suggestion. Never thought of doing that.

My brain just doesn't process scaling the way your brain does. I ask for help on scaling to colleagues and they ask me for help on things I'm good at. I love this forum!
 

Similar Topics

U
Scale a value 4-20mA on a 0-20mA input (Siemens)
I'm not sure of a scaling I did. I have a underpressuresensor that measures between -1 and 0 bar. Given by the sensor in 4-20mA. This goes into a...
2
Replies
24
Views
16,319
ason
A
U
Scale an analogue value
I have an extremely dumb math question. An analogue input gives me 0 to 27648 when operating in 0 to 20mA In the program I want to scale into...
Replies
11
Views
4,353
RRobbins
RRobbins
A
scale
the scale occasionally stops working and displays the message "no response from modbus" on the control screen . tunaylar - load line2
Replies
2
Views
140
danw
danw
S
PLC for small-scale production
Hi! I'm wondering if PLCs are used for small-scale production. I've got four machines doing different things with textiles, and I'm exploring the...
2
Replies
16
Views
1,339
I_Automation
I_Automation
J
Micro850 Serial Write to Scale
I am having an issue writing a carriage return to my scale, I can manually push the print button the the scale and then read the buffer. The scale...
Replies
4
Views
1,116
JustinEnders
J
Back
Top Bottom