how to realize More channels 4-20mA current loop output

[Candy Yu]

Dear Sirs,

I have a question,we have a 4-20mA input,4-20mA out,24V power product,but my client need two 4-20ma output at the same time ,and on a broad.pls someone tell me the circuit.Thanks.

Cheers!

Candy

[Henrik_Volkers]

http://en.wikipedia.org/wiki/Current_mirror

[frank_h]

Hi,

   With an analogue data transmitter module from TURCK you can solve your application.

   Take two IM31-11-i modules from TURCK. Connect the 4-20mA output of the 1st module,

to the 2nd module, so you feed the current trough both modules. Then your original 4-20mA

is found at the output of both module 1 and 2.

   Here is the TURCK Website:  http://www.turck.de/en/

________________________________________________________________________________________________________

http://www.industrial-automation-hands-on.com/

Message Edited by frank_h on 10-29-2008 07:49 AM

[K C]

..and if you want to feed more then one input you can also put two or more inputs in series. As long as the total resistance is not higher then specified by your source.

[Candy Yu]

Thanks.now i design a two output circuit: Pls check it,and see whether it is right.

[K C]

Hi Candy,

It is almost right, I think. Why the diodes at the inputs.

When I look at the datasheet of your isolator (I only can read the figures not the characters  ) the input is 50Ohm. So the input voltage (across the diode) is 0.2-1V. The 1N4007 starts to conduct at 0.6V.

Message Edited by K C on 10-31-2008 08:26 AM

[Candy Yu]

Thanks,KC. our this series input resistance is 50 ohm(max),when 4-20ma signal input,the input voltage across the diode is 10mV~50mV. Cheers! Ms. Candy

[Candy Yu]

Dear Sir, sorry,i have another question,still about 4-20ma signal,can supply power to two wires sensors.but its accuracy is so low,only 0.3%~0.4%, but generally need 0.2%.we are thinking of many ways,but still have no effect.

[K C]

Hi Candy,

According to Ohm's law (at least at this side of the world ) a current of 4-20mA through a 50Ohm resistor gives a voltage of 0.2 - 1V

Please explain your value of 10-50mV

I do not understand your second question. A accuracy of 0.3-0.4% is rather good I think for transmitters.

Message Edited by K C on 11-03-2008 08:34 AM