Grabbing a Baseline Value using RLL in Studio 5000

I'm looking at trying to program Relay Ladder Logic to average out a value for X amount of time.

In this application I'm looking to have an output set at 30% over "Value X". I want value X to be set by taking 15-30 seconds of live data and averaging out the data.

I was wondering how I would attempt to set this up in Relay Ladder Logic. Currently I was considering Having 5 Timers set for 5 seconds each and while each timer was running write the measurement value to a tag. Then after the 25 seconds I would average out the 5 values I'm left with and set that as my Value X.

Is this the a feasible way to approach this application?

Thanks,

David

sure, give that a try and post the code here if you want feedback.

Perhaps use one timer, move the values into a shift register of x number of readings then add them all up & divide by the number of shifts. So for example, you shift the value into a shift register every 5 seconds with a shift register of 5 words long, add them up & divide by 5 you have an average over the 25 seconds. Caveats: when you start the average value would be based on the values in the shift register either from the initial start up of all registers at 0 or if the system has been powered down then the values would be as per last run and not reflect current situation. Some PLC's have an average function built in.

parky said:

Perhaps use one timer, move the values into a shift register of x number of readings then add them all up & divide by the number of shifts. So for example, you shift the value into a shift register every 5 seconds with a shift register of 5 words long, add them up & divide by 5 you have an average over the 25 seconds. Caveats: when you start the average value would be based on the values in the shift register either from the initial start up of all registers at 0 or if the system has been powered down then the values would be as per last run and not reflect current situation. Some PLC's have an average function built in.

Click to expand...

I'm not familiar with using Shift functions. My PLC programming training was very basic covering the simple functions of RLL.

perhaps, you can try with one timer and and array.

Create an array, say 5 elements, and an int variable called index.

Set index to 0.

When timer is done first you will move your value into array[index] and then increment the index by one(ADD function).

When index is 4 or greater then move 0 to index.

It will work in a loop so in your array you will always have last five samples.

You can use AVE function to average.

Hope this helps

+ @Chopin

chopin said:

perhaps, you can try with one timer and and array.

Create an array, say 5 elements, and an int variable called index.

Set index to 0.

When timer is done first you will move your value into array[index] and then increment the index by one(ADD function).

When index is 4 or greater then move 0 to index.

It will work in a loop so in your array you will always have last five samples.

You can use AVE function to average.

Hope this helps

Click to expand...

I looked into the array function on Studio 5000 and I'm a bit lost on how to code this using Studio. I haven't necessarily messed with Arrays any so this is all a new concept to me.

Thanks.

No need for a shift register. Zero a DINT register (or REAL if using fractional measurements). Add measurement in x number of times. Then divide total by x.


If you want to do it again then just zero the register and start again.

If I wanted to post code for review is the best option just to post screencaps of the code in question?