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September 25, 2017, 11:56:39 am


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Author Topic: reading load cell with brx  (Read 602 times)
maciek
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« on: April 19, 2017, 08:04:29 pm »

what would i use to read a load cell that has 3mv/v output and 10v excitation 
any suggestions
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Controls Guy
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Darth Ladder


« Reply #1 on: April 19, 2017, 11:02:00 pm »

Signal conditioner.   ADC alone has two series.  Get a 4-20ma output and wire it to the PLC.
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I retract my earlier statement that half of all politicians are crooks.  Half of all politicians are NOT crooks.  There.
Evilbeard
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« Reply #2 on: April 21, 2017, 07:23:31 am »

Signal conditioner.   ADC alone has two series.  Get a 4-20ma output and wire it to the PLC.

I like to get the programmable ones, that way I have access to everything I could ever need. (dont' forget the programmer!)

« Last Edit: April 21, 2017, 07:26:12 am by Evilbeard » Logged
maciek
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« Reply #3 on: April 21, 2017, 06:11:09 pm »

thank you
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maciek
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« Reply #4 on: April 22, 2017, 10:22:35 pm »

i looked at the specs of that signal conditioner and it doesn't say about millivolts per volt 3mv/v like what the load cell puts out
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b_carlton
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« Reply #5 on: April 23, 2017, 10:21:06 am »

No, it doesn't appear to be a load cell conditioner. The APD-4051 from API (https://api-usa.com/pdf/api/apd4051.pdf) is similar to what you want though it is incredibly difficult just to find a price. AutomationDirect spoils us.
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An output is a PLC's way of getting its inputs to change.
plcnut
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« Reply #6 on: April 24, 2017, 04:21:32 am »

I am not sure what you are trying to do with a load cell, but it may be wise just to attach the load cell to a scale head and then read the weight from that. This may me necessary for working with scales that must be legal-for-trade. There are also these or these from Futek.
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~Jason Wolthuis
Controls Guy
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Darth Ladder


« Reply #7 on: April 24, 2017, 12:18:15 pm »

i looked at the specs of that signal conditioner and it doesn't say about millivolts per volt 3mv/v like what the load cell puts out

"mv/v" is not a signal format, it's a hardware characteristic of the load cell.  Feed it 10v, or whatever is within it's range, then take the 0-30mv full scale (or 0-[3 x excitation voltage]mv) and isolate/condition that with the signal conditioner to 0-10v or preferably 4-20ma.

Some thermocouple modules will even handle mv signals (such as from high current DC shunts, etc.) directly, but it's kind of hit and miss how well it works, so I'd stick with the signal conditioner.  IIRC, you're doing this in a BRX, which at this time doesn't have any [local/native] thermocouple inputs anyway.
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I retract my earlier statement that half of all politicians are crooks.  Half of all politicians are NOT crooks.  There.
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