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RecoveringA55hole

Flow sensor integrated into the current process

11 posts in this topic

Hi, I'm obvouisly pretty new to programing and automation. i was looking to get some helpful hints and maybe some steps in terms I could interpret. My current set up as followed, I have clean filtered liquid product being deposited into 5 tanks. I had a problem with one of my solenoid valves at tank 3 and didn't realize that tank wasn't feeling up. I don't want to drill into the tanks to put any level instruments in it. I have a paddle flow sensor and wanted to put a tee in the begining of the process line before it branchs out to moniter the flow. I want to be able to have an adjustable low flow alarm set point on the HMI. I don't need to log any data, I just want a live flow figure as I run every process and have an alarm come on if the flow drops to a certian figure for X amount of seconds... and possibly turn off the process if the alarm is activated. a Tag for the HMI? Micrologix 1100 Bul. 1763 ser. A Signet 2536 Rotor-X Flow Sensor (going on a 1/2" PVC pipe, K-Factor = 1027.1) http://www.signetins...df/2536spec.pdf http://www.signetins...pdf/2536eng.pdf Signet 9900 Transmitter (if i even need it) www.signetinstrumentation.com/pdf/English_Manual.pdf I'm willing to compensate anyone for some in depth advice if anyone is willing to take the time via email or PM. Thanks in advance. Edited by RecoveringA55hole

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I'm posting this on a different forum as well. Also, sorry for all the grammer errors. My fingers aren't meant for a little phone! Edited by RecoveringA55hole

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If the flow switch sends out a pulse every turn, you can put that into one of the high-speed inputs on the ML1100 and use that information to figure out the flow rate. If you use the transmitter, you can wire it to the analog input, just be aware that the input is 0-10V, not 4-20mA. Otherwise sounds like you're on the right track. Keep posting questions here, and we should be able to help.

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Ross, Thanks for the response. That's the thing, I'm clueless when it comes to how to write a program to retrieve the data from the flow sensor. My PLC programming experience consist of simple inputs activating outputs...nothing complex

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If you're measuring flow rate rather than volume, then the analog is the preferred method, as it would be simpler to program. There is a built in analog input on the ML1100, but it's only 0-10V, and the transmitter you are speccing looks like it's 4-20mA, which is typical. See if you can get one that is 0-10V, or you may need to get an analog input card for the ML1100. You can use a resistor to switch the voltage input to current, but you lose resolution. You would start be scaling the output of the meter to cover the range you want to measure. This might be how you order the meter, or you may be able to change parameters, depends on the meter. Say you are measuring 0-100gpm, and you have a 4-20mA signal. 4mA would be equivalent to 0gpm, and 20mA would be 100gpm. On the PLC side, you would see that signal as a raw integer value. Actual numbers depend on the hardware and the configuration, but you might see a value of 4000 to 20000, where 4000 is 4mA and 20000 is 20mA. You would then scale that using an SCP instruction so that you see a value of 0-100gpm. Make sense? You can display that scaled value on the HMI, and use compare instructions for the alarm. You would get an raw integer value in the PLC representing the signal from the meter. The actual numbers would depend on how you set up the analog input, but a typical range would be 4000-20000 where 4000 is 4mA

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Ross, Thank you. I'm going to purchase an analog input card to add on to my final slot available. I'm going to go with a 1762-IF20F2 analog input/out module because it is my only slow left for a card and I still need another output for my alarm light?

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A PID would be used if you're planning on controlling something, such as flow into the tanks or level of the tanks, with a control valve or variable speed drive (pump). If that's not the case, then no, a PID would not be useful. Are you pumping into these tanks or gravity fed? Also, for future ref, you don't necessarily have to drill into tanks for level information. Depending on what kind of tanks they are, i.e what material, open or closed top, etc. and whether you need point level, as in a high/low level switches, or continuous level, as in a constant level measurement (in feet, inches, % full, etc), there may be other options.

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I wouldn't be controlling anything with the flow meter, just want to show a display of the current flow rate and be able to set a low set point. If it drops below that while its running, shut down the pump or the whole program and trigger the alarm light output. I know i'm probably just repeating myself here, just really new to this and trying to grasp this simple project.

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Are you saying that you plan to use one of the outputs on this card for your alarm light? This card will have analog output, not digital so that may not be what you are expecting. (just so you know) On the other forum you say that you plan to use 1762-IF4 so maybe you found a digital output for your alarm light already?? BCS

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