Omron CP1L multiplying

[BAT]

Hi!
Newbie here...
Cx-programmer
CP1L PLC
NB7 HMI

I want to multiply something i by 1,5 in CX-Programmer to get a higher number to use in HMI.

Example:
-I have a 4...20mA scaling in a function block that gives me the GRAPH with +0...+1000.
-I want the output in the function block to be multiplied by 1,5 after scaling is done.
-So that when output is ex 500 my sourceword is 750, and when output is 1000 i have sourceword 1500

I might be dumb, but I am in a learning process

[drbitboy]

Welcome to the forum.

I see there are several multiply instructions in CP1L; see here: https://assets.omron.eu/downloads/ma....pdf#G10.33720

and here: https://assets.omron.eu/downloads/manual/en/v1/w451_cp1_cpu_unit_programming_manual_en.pdf#G11.57 824

and here: https://assets.omron.eu/downloads/ma...D847.CS1H.Only

But we don't really have enough information to answer the question e.g.

• Do you want to change (overwrite the 50% larger product to) the output value of the scaling function block itself, or do you want to write the product to a new location?
• What type of data are being multiplied, single or double, signed or unsigned, binary or BCD or floating point?

If you make a screen dump of the relevant section of the program, and annotate it to answer the questions above, it might help get a better answer.

[gclshortt]

https://accautomation.ca/omron-cp1h-math-instructions/
The above post will discuss the math instruction in the CP1.
This is a link to the entire series.
https://accautomation.ca/series/omron-plc-cp1h-series/
I hope this helps you out.
Regards,

[BAT]

Thanks for Reply!

See picture. This is what I want, but I get the wrong result word. I have tried with other numbers in the "first multiplier word" too.

* and *D Will not let me use "," in my numbers. Meaning no decimals.

-I want to write it to another position. You can see I take one word, and multiply it by a constant, and want a result word for further use.
-I think you get the other answer on the picture aswell

[drbitboy]

Have you tried

• 1.5

instead of

• 1,5

?

Also, the multiplicand appears to be an integer, the [*F] instruction might require casting it to a floating-point value, and you can then then cast the floating-point result from [*F] back to an integer; this approach would take three instructions.

Another approach that needs only two instructions would be to use a signed multiply by 3, then a signed divide by 2.

[BAT]

"Another approach that needs only two instructions would be to use a signed multiply by 3, then a signed divide by 2."


This worked ofc!
Thank you for just doing it simple

[drbitboy]

I am glad that worked out!

TL;DR

Another way to express 1,5 without commas or decimal points is 15e-1

Although given the example, where F* takes arguments of 1000 and 1,5 multiplies them, and gives a result of 750, makes me wonder what else is wrong with that processor/language/brand of plcs.

Or maybe the problem was using an integer value for the multiplicand and/or product in a floating-point instruction; in a CX-Programmer manual, I found this:

xxx.png

[parky]

Most PLC's to do floating point maths you must make the two variables into floats. so for example if you have a raw analogue this would probably be a 0-32000 or what ever, convert it to a float (some call it a real) then do the maths.
Using PLC's like Omron & Mitsubishi where the registers are 16 bit floats use 2 16 bit registers, I do know that Mitsubishi will not compile if using symbols that have been declared as integers or words in a floating point maths function, however, using direct registers like D100 will assume the float value would be in D100 & D101, so it will compile but give the wrong answer.