Percentage failures for AB 1500

Any ideas on best way to sample pass / fail counts over 100 or 1000 pass fails so I can monitor percentage failure rates on a reject conveyor system and display it on my hmi ... Bring next result into a fifo or something and push oldest out and work out percentage of fifo passes ...Any ideas appreciated

Hi Keith

I have done this using 2 counters (or an add instruction) 1 for good parts and 1 for bad parts. I use a cpt instruction then to do the math for the batch.
for the last 1000 parts I would let the counters count until the good reached 1000 and then count down the bad until it's zero or I get a bad part where I would add 1. The good would stay at 1000 untill the batch Is over or the shift or whatever you what to use to reset it.


Donnchadh

Welcome to the forum! I've done it a lot on RSLogix 5000 PLC's, but not on an old ML1500. Although the concept would be the same.

Set yourself up an array, then each time a sample is taken do the following:
1. Check for good/bad. If good, do nothing; if bad, add 1 to a counter or integer
2. Check if the FIFO is full (.DN bit set). If not, skip step 3 and go straight to step 4
3. Unload the FIFO and check the unloaded value. If it represents a good sample do nothing; if it represents a bad sample subtract one from your counter/integer (as this bad sample is now no longer within the last 100 samples and shouldn't be counted any more)
4. Load the FIFO with your latest sample result
5. Do a simple calculation comparing your counter/integer value with the total number of samples that you're comparing (i.e. 100 or 1000) to work out the percentage good/bad
6. Attach electric cattle prod to sampling operator and trigger if sampling success rate drops below 75%
7. Profit!

(steps 6 and 7 optional. Especially step 7)

Hope that gets you started!

Thanks I will try this sorry for delay out of country let you know how it goes thx again