Analog scaling techniques

Could I get a few examples of analog scaling techniques from the Users? In the past, I have used equipment that did this for me automatically. I am using a GE Fanuc 90-30 with VersaPro and need to scale some 4-20mA inputs to engineering units, for example, 0-100 or 0-1000. Thanks,

There are a couple of ways to configure 4-20 mA inputs, but let's assume you've selected the configuration where a 4 mA signal gives you a %AI value of zero and 20 mA gives you a %AI value of 32000.

If you want the data scaled over a range of 0 to 1000, you need to multiply the %AI value by the scale factor of 1000/32000. This is easier if you first convert the %AI value to floating point.

That covers the specific case where a value of zero in the scaled data corresponds to a value of zero in the unscaled data. The more general case of the scaling equation is Y = mX + b, where Y is scaled data, X is unscaled data (%AI data), b is the scaled value when the unscaled value is zero, and m is the ratio:

(Max scaled value - Min scaled value)
----------------------------------------
(Max unscaled value - Min unscaled value)

If you don't have a CPU that supports floating point arithmetic, you need to convert all of your values to DINT (32-bit).

abrier said:

Could I get a few examples of analog scaling techniques from the Users? In the past, I have used equipment that did this for me automatically. I am using a GE Fanuc 90-30 with VersaPro and need to scale some 4-20mA inputs to engineering units, for example, 0-100 or 0-1000. Thanks,

Click to expand...

I think there is one who post to my forum "Free Software". Try to visit www.plcman.com and look for downable item there. It is in an excel form and the title is "Conversion: Milliamps - PLC Raw Counts - 1 to 5 vdc - Percentage" Hope this one gonna help you...