convert 4-20mA to 0-5volt!

L

leyla

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?

A

Anonymous

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.

M

musta maakkara

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

K

kamran

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

O

oldman

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.

M

millie

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.

L

leyla

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

S

Steve Young

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.

A

Anonymous

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.

C

Curt Wuollet

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)

J

Joe Jansen/ENGR/HQ/KEMET/US

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

D

Dr. R. Erlich

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

C

Candy Yu

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&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.

S

stouras

please can you sent me the circuit too.
[email protected]
thanks

S

E

Engineer

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.

K

krishna

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: [email protected]
thanks!

C

Curt Wuollet

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

A

Alan Balcombe

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?