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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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7th Oct 2017, 3:26 pm | #1 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
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Loop Calibrator Project
Hello,
Has anyone here ever made their own loop calibrator? As a project on the side at home, I'd like to make one. So at the moment just gathering information and resource on one. Has anyone got any useful information which might assist? Thanks. |
7th Oct 2017, 4:59 pm | #2 |
Guest
Posts: n/a
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Re: Loop Calibrator Project
What is a loop calibrator?
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7th Oct 2017, 5:50 pm | #3 |
Octode
Join Date: Aug 2006
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 1,082
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Re: Loop Calibrator Project
do you mean a 4-20 ma calibrator ? if so then yes
you can do it easily or the hard way what do you need it for Trev |
7th Oct 2017, 6:34 pm | #4 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
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Re: Loop Calibrator Project
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7th Oct 2017, 9:10 pm | #5 |
Heptode
Join Date: Sep 2009
Location: Tonbridge, Kent, UK.
Posts: 685
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Re: Loop Calibrator Project
Made one when at work for checking PLCs. Simple two transistor adjustable constant current generator run off a 9v battery. Good enough for gross calibration error checking. I seem to remember it ran out of puff with some PLCs, probably should have used 18v.
gmb |
7th Oct 2017, 9:23 pm | #6 |
Octode
Join Date: Jan 2003
Location: Ashby-de-la-Zouch (it's not by the sea)
Posts: 1,254
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Re: Loop Calibrator Project
I guess something like this would work ok?
It might need a C across the output, but looks good to me.
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Now where on earth did I remove that from? |
8th Oct 2017, 10:02 am | #7 |
Octode
Join Date: Aug 2006
Location: Stoke-on-Trent, Staffordshire, UK.
Posts: 1,082
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Re: Loop Calibrator Project
all you need is a 24 volt supply a 470 resistor a 10 k linear pot and a multi meter on the ma range connect them in series and then measure the loop current using the ma range on your meter the 470 is to limit the shortcircuit current to 40 ma the 10 k pot will allow the current to be varied from 2ma up
very simple to make and use trev |
9th Oct 2017, 4:18 pm | #8 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,527
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Re: Loop Calibrator Project
The 10k pot will need to be rated at 4W or more so as not to exceed its current rating. The LM 317 route could well be cheaper if you need new parts.
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