from the None department...
convert 4-20mA to 0-5volt!
1 out of 1 members thought this post was helpful...
 Posted by leyla on 19 August, 2002 - 3:52 am
I want to convert 4-20mA (from a sensor) to 0-5Volt.
but I don't know how can I do it?
can I do it with a resistance (250 ohm) only?
can I do it with a opamp as a negetive feedback circuit?

1 out of 1 members thought this post was helpful...
 Posted by Anonymous on 19 August, 2002 - 11:04 am
I've seen many instances where a 250 ohm resistor is used. Just remember to scale your reading from 1 to 5 instead of 0 to 5 Volts.

 Posted by oldman on 19 August, 2002 - 5:10 pm
I've seen a 250 ohm resistor covert 4-20mA to 1-5 vDC most of the time thats the way to cal. input cards in your i/o rack without stoping or bumping a dcs system.

 Posted by musta maakkara on 19 August, 2002 - 4:59 pm
Hej!!
you cannot convert the signal to from 0 to 5 volts, since you do not have 0 mA but 4 means 0

you can convert 4-20 mA to 1-5 Volts with a precission 250 Ohms resistor. in parallel with the measuring device to read volts.

according to ohm's law, V = R(E)
thus,
.004 (Amps) times 250(ohms) = 1 Volt
.020 (Amps) times 250(ohms) = 5 Volts

if you need more...
musta_maakkara(at)hotmail.com

 Posted by IIvan on 8 August, 2012 - 8:42 am
>Hej!!
>you cannot convert the signal to from 0
>to 5 volts, since you do not have 0 mA
>but 4 means 0
>
>you can convert 4-20 mA to 1-5 Volts
>with a precission 250 Ohms resistor. in
>parallel with the measuring device to
>
>according to ohm's law, V = R(E)
>thus,
>.004 (Amps) times 250(ohms) = 1 Volt
>.020 (Amps) times 250(ohms) = 5 Volts
>
>
>if you need more...
>musta_maakkara(at)hotmail.com

All you say is wrong...

 Posted by kamran on 19 August, 2002 - 5:09 pm
Hi leyla,
Before giving the answer of your question I want to know that Why you want to convert mA to Volts, are you facing some problem or you want to install new one also explain its use and what type of Automation you have than I can give you the complete procedure.

Regards

kamran

 Posted by leyla on 20 August, 2002 - 3:15 pm
i have a sensor with a current output and i want convert it to voltage for ADC input. would you please help me more?

leyla:)

 Posted by millie on 20 August, 2002 - 10:14 am
I would always choose to use one of the many commercially available process converters.

These enable you to convert to any of the standard process control ranges, i.e. 0-20mA, 4-20mA, 0-5V etc etc.

They generally also include controls for adjustment of "Bias and Gain", this will allow any aditional adjustment to your required process control variable.

They are available in the UK for 50-100 GBP, I have used many over the years and have found them extremely useful.

 Posted by Steve Young on 20 August, 2002 - 3:42 pm
An off the shelf product from phoenix contact is available that will convert 4-20ma to 0-5volts, or most any other ma or voltage range you desire. It is not a cheap as a 250Ohm resister, but is very reliable, accurate, and user friendly.

 Posted by Anonymous on 23 August, 2002 - 3:25 pm
There are some more off the shelve solutions. Pepperl & Fuchs, Weidmueller and some more. Just check the companies dealing with intelligent clamps.

I always would use a commercial product if it is used in industrial environment, you have the support and the reliability of the producer.

But i would consider to use the 4-20mA instead of the 0-5V. The current based system is more stable and you can detect the failure of the sensor.

 Posted by Joe Jansen/ENGR/HQ/KEMET/US on 26 August, 2002 - 1:44 pm
This question or one just like it gets asked nearly monthly. PLEASE! Check the archives for answers to simple questions like this before
posting.

Also, understand Ohm's Law.....

a 250 ohm resistor across a 4-20mA signal will yield a 1 to 5 volt 'output'.

If that is close enough to 0 to 5, then that is all you need.

--Joe Jansen

 Posted by Curt Wuollet on 26 August, 2002 - 10:03 am
Check the archives: I've described how to do this with opamps at least twice. I'd mail you the diagram but it's on the computer at my last job. If you get stuck, mail me and I'll draw it up.
The principle is that you use the resistor then subtract the 1 volt and scale by 1.25. I really should do a small board for this and sell kits.

Regards

cww
(wideopen @ecenet.com)

 Posted by Hafeez on 13 June, 2012 - 3:31 am
> Check the archives: I've described how to do this with opamps at least twice.

Where are these in the archives can you give a direct link please.

Moderator's note: To search for old post, use the Search Box on the right hand side of the menu bar and search for the relevant terms. For advance search options, click the Question mark (?) next to the Search Box and follow the directions.

 Posted by beijing L888J888 on 14 April, 2007 - 1:01 am

 Posted by Dr. R. Erlich on 30 September, 2007 - 1:09 pm
Dear Leyla,

The following is a link to a industrial standard board that will produce 0-5V or 0-10V DC etc., from 4-20mA.

http://www.eidusa.com/Interface_Boards_Current_to_voltage.htm

This board is designed to perform industrial standard current to voltage conversion. Utilizing differential input Op-Amp, with both zero, and span adjustment. It is typically used to convert current (4-20mA)to a stable constant-voltage source.

A precision instrumentation amplifier and filter combination provides an accurate, conditioned ±10 or ±5 V output from a 4-20mA current input. The output voltage range is easily selectable via on board jumpers.

Ron

 Posted by Candy Yu on 12 January, 2009 - 10:20 pm
You only need a signal converter, about 4-20ma to 0-5v. Please check the datasheet:
http://www.szsunyuan.com/sy/product_list_2.asp?pageno=2&amp;Cid=129

But if you do it by yourself, the resistance 250 ohm is ok, and you need a DC/DC converter and capacitance and other IC.

Cheers.

 Posted by stouras on 26 February, 2009 - 11:27 am

please can you sent me the circuit too.
Stouraitisk@hotmail.com
thanks

 Posted by sella on 19 January, 2010 - 6:11 am
kindly send me the circuit diagram too,
sella [at] mail.idsesb.com.
my thanks

 Posted by sojua on 9 March, 2009 - 11:09 am
Can you please send me the circuit??
My email is sofcr05@gmail.com

Thanks a lot!!

 Posted by krishna on 9 April, 2009 - 5:01 am
could you please send me the circuit for converting 4-20 mA in 0v to 10v. I want to do it myelf on breadboard. Help me to list the componets required and procedure.

Plz send the data to my email: rkkntu@gmail.com
thanks!

 Posted by Curt Wuollet on 9 April, 2009 - 1:09 pm
Well, for 1-5 volts it's easy, 1, 250 Ohm resistor. For 0-5 you need a standard Op Amp difference amplifier which you can look up anyplace. Four resistors and an op amp plus any bypass caps, etc. On the inverting input you set up 1 volt with a voltage divider. You apply the 1 to 5 V to the non-inverting input. Both of these, the divider and the signal are ground referenced. The gain on the difference amp should be 1.25 so 0V difference gives you OV out and 4 V difference gives you 5 V out. Doing this for non ground referenced signals gets more complicated but, the principle is the same.

Regards
cww

 Posted by Evan Thomas on 15 July, 2009 - 3:20 am
Candy Yu,

Just new and just found what I have been looking for. I need to convert TWO 4-20 mA pressure transmitters so I can connect them to a Pico ADC-16 logger. Could you assist and send me a copy of the circuit Please.

Thanks
Evan Thomas
beckett [at] iinet.net.au

 Posted by Brian Sullivan on 26 November, 2009 - 12:08 pm
> You only need a signal converter, about 4-20ma to 0-5v. Please check the datasheet: www.szsunyuan.com/sy/product_list_2.asp?pageno=2&Cid=129
>
> But if you do it by yourself, the resistance 250 ohm is ok, and you need a DC/DC converter and capacitance and other IC. <
>

could you please send me the info, thanks
bsu [at] huber.co.uk

 Posted by abimanyu on 22 October, 2010 - 10:03 am

this is my email:
lottethief@gmail.com
thank before.

 Posted by Engineer on 12 March, 2009 - 7:23 am
I've seen that use 250ohm resistance to converte 4-20mA to 1-5 voltage but if you need to 0-5 volt you can use with op-amp.

 Posted by Alan Balcombe on 9 April, 2009 - 8:53 pm
Assuming there is/was (in 2002) a need to convert, and not just a "want"......

If the so called "sensor" gives 4-20mA, it's maybe not a sensor, but a transmitter. Then a question is: would you like the 4-20mA/0-5V converter to provide power for the transmitter, as well as doing the conversion?

Then maybe we could ask if there is a need to isolate the signal to protect the receiver, so maybe the converter should be an isolator too? Perhaps the signal also needs linearising, inverting, limiting?

It would be nice to know - after all this time - whether Leyla found a resistor or electronic module would do the job.

Alan Balcombe
Weidmuller
Richmond, VA

 Posted by Y.K.JARIWALA on 10 April, 2009 - 7:46 am
Use isolator/converters from Moore Industries. this is off the self product.

Jari

 Posted by Surya on 5 May, 2009 - 3:25 am
Hi,

You can do this scaling in a simple way. Use 250 ohms in your circuit for both the ranges (0 to 20mA and 4 to 20mA) .Now you will get (0-5V and 1-5V correspondigly).In software you can do the following to achieve this.

The formula used for this is : y=mx+c

Let x = 4 to 20mA , Difference is 16.
and Y = 0 to 4000 (12 bit ADC), Diff is 4000.

here you get m = 4000/16 = 250.

Now , y = (250)X+c
for y =0,
0 = 250 x 4+c
c = -1000
y = 250x-1000

Now with the formula y = 250x-1000, try putting x and y values.

Eg: when x = 4mA , y should be 0 counts right.
when x = 20mA, y will be 4000 counts.

Hope it helps..

Any querries email to : electrozeal@gmail.com

Thanks
Surya
India

 Posted by Roy Matson on 28 November, 2009 - 3:51 am
I hope the original poster has it figured out by now!
it's from 2002.
Roy

 Posted by Dilip on 28 November, 2009 - 8:23 pm
We are having Siemens S7-300 PLC with analog inputs. We are also using the same method to display desired range of values on HMI. Its a practically proven method.

 Posted by scadametrics on 30 November, 2009 - 3:40 pm
Count me among those who recommend an off-the-shelf solution.

Dataforth (www.dataforth.com) makes several 4-20-->0-5V converter modules.

One that I'm familiar with is the 8B32-01, but I believe they have other models, also.

They have a very knowledgeable outside national sales engineer: Bill McGovern 520-741-1404 ext.246

 Posted by Irish banana on 13 October, 2010 - 11:07 am
Hi

You can not convert 4-20ma to 0-5v easily, but with a 250 Ohm precision resistor you can. There is a simple math calc to check if your signal is correct.

4mA/100x25= 1V
20mA/100x25= 5V

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