Is my math right?

[kurt.brinker]

Just want to post back up and say i worked on this for an a little over an hour and got the program done and the PV setup. I downloaded it and it was a HUGE success. The meter gives me a pulse evry 3 pounds and my pulse width is 30ms. My lb setpoint is divided by 3 and placed into the pulse setpoint and my gallon setpoint is multiplied by density variable and then divided by 3 and that becomes the pulse setpoint. I only got to run 1 test but it worked perfectly.

the way i figure, my max will be 300 GPM with a density of 8. i will be at 1 pulse per 75ms. with a pulse width of 30ms, i think i will be fine.


everything look ok?

Thanks again for your help.

 

[kamenges]

That all looks reasonable to me. Nicely done.


Keith

 

[daba]

Kurt, just so you don't have to suffer this again next time.

Research how to use an STI program file, and put all your pulse detection/counting in the STI routine. It is the ONLY way you can guarantee seeing all the input pulses. Without an interrupt file, imagine if there was a conditional iterative loop in the code that stretched the scan time excessively, your input could have gone on and off several times.

mgvol suggests you consider using IIM, I suggest you MUST use it in your interrupt routine, otherwise the code is just going to look at input data updated at normal scan rates.

Your STI execution interval should be significantly less than your minimum pulse ON or OFF time, preferably about a half. Oh and don't forget to one-shot your input so you only count pulse transitions once, or use a counter to count the pulses (a counter has an inbuilt one-shot on its CU enable input).

HTH