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Help with s7-300 frequency measurement

Created by: Lawrenceb11 at: 4/9/2012 11:31 PM (4 Replies)

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4/9/2012 11:31 PM	Rate (0)
Lawrenceb11 Posts: 11 Rating: (0)	Hi , for a school project I need to to control measure and control a flow of water . I know how to make a PID in siemens already , all I need now is to read the frequency from my magnetic flowmeter , once I can read the number ill be good . Only problem is that I dont know how to do that . I have a cpu siemens 313-2-DP and am trying to measure the frequency , I am wondering what exactly should I write my wired adress 124.0 to the SFB48 block , I dont understand this thing W#16#300 , it makes no sense ... All images here show my setup , am I good to read the frequency in MEAS_VAL once I give the block the correct input adress ?? all images explain what I have done so far , only need a few more pointers then I believe I will be able to make this work ?? I am using an example program , is it necessary to have an OB1 and FB2 wich are identical , I read this from siemens FAQ . Am I doing this right ? Attachment PLCadresshookup.JPG (377 Downloads)
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4/9/2012 11:33 PM	Rate (0)
Lawrenceb11 Posts: 11 Rating: (0)	other image Attachment HWconfig.JPG (316 Downloads)
Lawrenceb11 Posts: 11 Rating: (0)
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4/9/2012 11:34 PM	Rate (0)
Lawrenceb11 Posts: 11 Rating: (0)	another image Attachment OB1FB.JPG (299 Downloads)
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4/9/2012 11:36 PM	Rate (0)
Lawrenceb11 Posts: 11 Rating: (0)	another Attachment sfb48.JPG (294 Downloads)
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4/10/2012 7:47 AM	Rate (0)
umencho Diamond Member Joined: 3/21/2006 Last visit: 3/30/2025 Posts: 10239 Rating: (1183)	Hello, In your case address should stay W#16#300 as the address in hardware configuration is 768 (by deafult too). So, 768 in HEX is 300. In FB2 you are calling for SFB48 in order to read the pulses. In order to execute cyclicaly this FB you should call it in OB1. If you didn't call it in OB1 this FB will not be executed. Best regards, Hristo Mihalev

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