4-20mA Precision Source Ideas

John Devereux · 2011-04-22T06:57:04+00:00

Hi,Anyone have any ideas for a good "4-20mA" driver circuit? I want toconvert 0-2.5V from a DAC into 0-25mA, driven by 9-36V supply.I have a circuit that works well, see below LTspice netlist, It'sbasically National AN1515 fig 6 "improved howland current source" with atransistor added to offload the power dissapation.Only drawback is it uses a lot of precision resistors. Is theresomething that uses less resistors (and more opamps perhaps?). Seemslike it should be possible with just one precision part.Thanks,JohnVersion 4SHEET 1 2076 1524WIRE 224 -48 -96 -48WIRE 400 -48 224 -48WIRE 176 64 160 64WIRE 272 64 176 64WIRE 512 64 352 64WIRE -96 80 -96 -48WIRE 400 112 400 -48WIRE 224 128 224 -48WIRE 176 144 176 64WIRE 192 144 176 144WIRE 336 160 256 160WIRE 192 176 160 176WIRE 160 224 160 176WIRE 224 240 224 192WIRE 400 240 400 208WIRE 512 240 512 64WIRE 512 240 400 240WIRE 400 256 400 240WIRE -64 368 -96 368WIRE 64 368 16 368WIRE 160 368 160 304WIRE 160 368 144 368WIRE 192 368 160 368WIRE 400 368 400 336WIRE 400 368 272 368WIRE 592 368 400 368WIRE 592 416 592 368WIRE -96 432 -96 368FLAG 80 64 0FLAG -96 160 0FLAG -96 512 0FLAG 592 496 0FLAG 224 240 0SYMBOL res 160 352 R90WINDOW 0 0 56 VBottom 0WINDOW 3 32 56 VTop 0SYMATTR InstName R1SYMATTR Value 10kSYMBOL res 288 352 R90WINDOW 0 0 56 VBottom 0WINDOW 3 32 56 VTop 0SYMATTR InstName R2SYMATTR Value 10000SYMBOL res 384 240 R0SYMATTR InstName R3SYMATTR Value 100SYMBOL res 256 80 R270WINDOW 0 32 56 VTop 0WINDOW 3 0 56 VBottom 0SYMATTR InstName R4SYMATTR Value 10kSYMBOL res 64 80 R270WINDOW 0 32 56 VTop 0WINDOW 3 0 56 VBottom 0SYMATTR InstName R5SYMATTR Value 10kSYMBOL npn 336 112 R0SYMATTR InstName Q1SYMATTR Value MJD31CSYMBOL voltage -96 64 R0SYMATTR InstName V1SYMATTR Value 40SYMBOL voltage -96 416 R0WINDOW 123 24 132 Left 0WINDOW 39 0 0 Left 0SYMATTR Value2 AC 1SYMATTR InstName V2SYMATTR Value PULSE(0.4 2.0 100m 1u 1u 100m)SYMBOL voltage 592 400 R0WINDOW 123 0 0 Left 0WINDOW 39 0 0 Left 0SYMATTR InstName V4SYMATTR Value...

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TralfamadoranJetPilot 15 years ago

You have two choices. Either YOU are then obsolete as well, you decades old dumbfuck, and you should go kill yourself, OR you realize that not only is it decades old, it has SURVIVED the decades, and IS the STANDARD teaching model and engineering model in the ENTIRE industry. And YOU are NOT. About the only thing you ever taught was your daughter how to be as big an asshole as you.

You are full of s*it, and if you were actually a man, I'd knock it out of you. Since you are a pathetic child, I'll sit here and laugh. You are so wrong, it shouldn't be funny. That is sad.

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hifi-tek 15 years ago

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John Fields 15 years ago

I do, and I also draw them the same way for use in presentations.

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John Larkin 15 years ago

Amateur?

John

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Rich Grise 15 years ago

Boy, you sure are a f*****ad.

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The_Giant_Rat_of_Sumatra 15 years ago

I am more than a little confident that God will forgive me my tiny verbal indiscretions, while the sins you sport will likely cost you, because you are too arrogant to ask The Lord to forgive you as your heart is on its last few beats. And you likely sin every day, and are too stupid to even know it. Your post here, for instance.

And on top of all that, it is also obvious that you do not even know who George Tirebiter is. You are definitely going to Hell. Bwuahahaha!

I suggest you start with

"Waiting For The Electrician, Or Someone Like Him"

Then

"Don't Crush That Dwarf, Hand Me The Pliers"

Then finish with

"I Think We're All Bozos On This Bus"

I doubt you have the right stuff to get it though.

So, Player... click click, you decide... Death, or Chi Chi?

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TralfamadoranJetPilot 15 years ago

Jeez, you really do need it.

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krw 15 years ago

Fields, you're as stupid as AlwaysWrong. Four-way junctions, with dot, *ARE* industry standard.

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John KD5YI 15 years ago

Your reply makes you a hypocrite of the worst kind. You and your ilk are always condemning others for their behavior while justifying your own behavior as presented here.

I do know who he is and he barked to me that your are his offspring by a bitch who committed suicide because she gave birth to you. Of course, George also committed suicide (by chasing cars) due to his embarrassment at fathering you.

Have a nice day, AlwaysHypocrite.

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John Larkin 15 years ago

Anything I do, JF finds fault with. I can have a lot of fun with that.

John

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Rich Grise 15 years ago

But still, there are people who separate one of the conductors, just for unambiguity's sake, i.e., instead of this:

| | | --------o------ | | |

they'll do this:

| | | -----o--o---- | | |

Cheers! Rich

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JohnS 15 years ago

john Have you looked at the Burr Brown part XTR115? Used these to good effect in 4/20 mA sensors with added transistor to keep dissipation low in I/C. Regards

JohnS

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The_Giant_Rat_of_Sumatra 15 years ago

You really have to be a complete loser to ascribe a standard to a faulty behavior.

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John Fields 15 years ago

I'm sure you think it must be from hearing it so often, but no; the magic word is "please".

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The_Giant_Rat_of_Sumatra 15 years ago

Perfect.

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John Fields 15 years ago

I see you believe that a pound of cure is worth an ounce of prevention.

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John Fields 15 years ago

:-)

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John Larkin 15 years ago

How about "coward"?

I post real schematics and real PCB layouts. Why can't you? Or your new pal AlwaysWrong?

John

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John Larkin 15 years ago

Bunch of old hens whose claws can't hold a mouse.

Post some schematics or cluck. Your skill set suggests you'll keep clucking.

John

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Spehro Pefhany 15 years ago

There's an image I didn't need.

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4-20mA Precision Source Ideas

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