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hotwires last won the day on March 29

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About hotwires

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  • Birthday 03/29/1981

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    land mobile radio, amateur radio, flying single engine aircraft

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  1. Ausman's suggestion for using an interrupt for a precise 2.5 mS time base is an excellent idea. The whole thing was new to me. The Vision help section was well versed on the topic and answered my earlier question as to whether or not the subR required a ladder call. -hW Cara, The contraindication (let's not use the word bug) in visilogic is that in Ausman's "pumpexample2.vlp" the project optimizer shows a warning that a routine is not called in ladder. Fundamentally it's output is true, however inerrupts are an exception and do not require a ladder call. It appears the project optimizers code is not self aware of this. It's just evaluating subR's and their associated ladder calls. the program loads and functions fine. Thanks all for the clarification on what defines enhanced Vision hardware. -hW
  2. Program works in SM43. I'm NOT calling the interrupt subroutine. I'm just saying that the project optimizer is not "self aware" that "_interrupt" don't need to be called. No harm done. It could be a source of confision for someone who always runs the project optimizer and follow it's advice.
  3. It's doesn't prevent download, just states that the subroutine is not called, optimizer logic is not recognizing that the _interrupt is "self called". Program works. I added a comparator to zeroize stored count if 2.5mS counter exceeds 24,000 (less than 1 GPM). The update time and flow rate are directly proportional. cruises along nicely near 60 GPM. 2 GPM update time 30 sec, 1 GPM: 60 sec. that's the laws mathematics at work. Works better than counting pulses for a 60 sec interval for every sample. Thanks All
  4. correct, no comilper error. Just project optimizer. Hope to try it tonight live in the OPLC.
  5. Aus, Thank you for the .vlp, I'll try it in my "R&D" Samba 4.3" This may be a silly question: Does the subroutine: "_Interrupt 2.5 mS" have to be called in the main routine? Or does the _ make it run irregardless? The project optimizer flags it however after reading the help section it appears the name makes it run without a call. Looks like the theoretical resolution would be 0.15 GPM That will be more than sufficient! Is an SM43-J considered an enhanced Vision on NOT? Love the simplicity of your program!!! I'll be honest, my conceptual approach was a bit more complicated. Simple is good. Thanks, HW
  6. The pump runs 24/7. So demand bit wouldn't be a useful zero signaling bit. Zero flow would only occur during power failure (which could be detected) or: pump failure, pump sucking air, discharge side occlusion, flow meter failure, unauthorized valve closure between disharge side and meter input flange. I'm sure there are a few possible conditions I've missed. My approach for testing logic is to present every possible set of conditions and then observe results, then ask: Is this what I wanted to happened?
  7. i use ptc for totalizer counters. I'm new to the pulse to gpm conversion with (relatively) real time updates. I took the freq counter logical approach but quickly found anything less than a 60 sec sample wasn't gonna be accurate down to the gallon. I seen in one of the examples where they use an output on plc to simulate pulses. I'll have to try that out. don't think my analog function generator will go low enough, 1 Hz would be 60 gpm. i've got a plc on my bench to play with but not the meter. i'm pre planning this project, no trigger pull on it yet. anytime I learn something new it's not time wasted. all prior flow meters I've worked with have had a 4-20mA gpm scaled output and programmable pulse:gallon ratio (and pulse duration).
  8. thinking about how it will need to handle a zero flow condition. the count would just keep running depending on where the disc stops and in what state. that's where limit setpoints come in. not exactly simple, but as the saying goes: "if it was easy anyone could do it!"
  9. A Tektronix 422, how ever did you know! Very compact scope back in it's day. Still works great. Never used interrupts on a PLC, kudos for the inspiration! I'll have to go spend some time in a pumphouse to examine the flowmeter, I don't have it's twin on my office desk Just did a walk thru a few days ago to see what all client had to work with and wanted to see in an automation solution
  10. i believe what you are suggesting paralells my idea of measuring the "period" (time between pulses) and using math to equate to flow rate. the most instantaneous and accurate possible measurement is the time between two pulses, which would vary proportionately from 0 ms (0 GPM) to 1000mS at 60 GPM. haven't had the flowmeter cap detached yet. 1 PPS is great for a totalizer but not so great for instantaneous flow rate. I started in the frequency counter mindset, count pulses for defined sample interval. that leads me to a 60 second sample being required to get 1.0 gallon resolution. frequency i'm trying to measure is to low for that approach. using the counter method: wouldn't the scan time be a factor in the rate of incrementation? one PTC would latch a contact to a counter and the next would release it, then store that counters value, and reset it? I'm assuming (perhaps incorrectely) that the pulse duration is constant, only the time between pulses changes with flow rate. But the more I think about it: if it's a magnet on a rotating disc then velocity would affect pulse ON time duration. Haven't examined the mechanics of the meter.... so not sure. read the help (and hardware installation diagrams) on the vision HSC. For some reason I'm not making the connection on how I use the in0 and in1 as a reset when I only have one pulsing line from meter.
  11. Cara, Ultimately both. I'll take whatever I can get, whenever I can get it. Most all the the Linux embedded security camera DVR's have auto DST offset, user specifies the day, week, month of beginning and end, the offset in hours, and time to execute (in 24 hour). One day of collected data will be an hour lean or an hour heavy, but at least it's just twice a year. I was two days late manually intervening this time around. If a person was managing 100 OPLC's without remote access it would take all day to do DST corrections.
  12. Community, I'm experimenting with a program where I need to convert a pulsed flow meter signal into GPM. No big deal, right?! Here's the catch: the turbine style flowmeter is calibrated at 1 pulse per gallon. The well flows right around 60 GPM 24/7. There is a self contained totalizer at the site now that is "jittery" in it's GPM indications. I already know all the ways I could count pulse or measure frequency and factor my way to GPM. With a range of 0 to 100 GPM at 1 pulse/gallon what is the best way? The shorter the sampling period the higher the multiplication factor and the poorer the instantaneous resolution becomes. A 1000mS sampling with about a pulse per second has a resolution of nearly plus/minus 60 GPM ? which is not so useful. Doubt that changing the flow meter to a unit with pulsed and 4 to 20 mA is in the cards. I have a feeling I have answered my own question already with the laws of physics. Any comments, ideas, or remarks are welcome. Sincerely, -HW
  13. Long live the PLC5 (SLC500) line! A real workhorse. Not cheap and doesn't always play well with others but it certainly deserves its place in the PLC Hall of Fame.
  14. They have the 50 or 60 Hz noise rejection settings on Unistream 8 ch AI, I suspect it is a software based notch filter. A ladder based filter while not impossible would be a bit over my head. Good notion, Nobody likes false alarms or measurements!
  15. Yes, it has that inherent tendency to send us all crazy once in a while! And as always thank you all for sharing your knowledge! Be it expert or novice, it's all appreciated.