In LOGO 8 how do I take a figure from a mathematic instruction and continuously add it to the next figure to give a total at the end. The figure will be a measurement from an Anolog input going to a Anolog amplifier to give me a distance from a 4-20mA sensor

Thank you I'm only getting back to this now. In my process I take my 4-20ma signal and turn it into a measurement. This bit is ok by using an Anolog amplifer. I then have a mathematic instruction to do on this, so it will be a predetermined distance "10000mm" - my signal length " anything up to 5000mm" this will be the Figure I will want to continuously count until I get a total at the end of a run so I presume I will have a second mathematic instruction to do

What I want to do is measure a board using a Keyence sensor with a range of 0-5m on 4-20ma. I have a mechanical stop 10m from the sensor. If a board was to stop and the sensor sends a signal of 12ma I know that it's 2.5m from the sensor leaving the board 7.5m long (10-2.5). This is the measurement I want to continuously add up. I hope this makes sense.

Hi, 

If I understand your "problem" you need the following mathematic instruction:

Lenght of board = 10m - measured length. 

 I've made a small sample were I scale the 4..20mA to 0-500 (so 1 point for each cm). 

The I make a mathematic instruction which is always enabled. 

In this instruction I set the value to 1000 (= 10meter) and subtract the value of the sensor. 

So in your case if I have 12mA (which is 250 in my example) the output is 750cm which is 7,5meter. 

You can play with the scaling to get it to meters or something you like. 

Does this help?