convert current signals

[Pandiani]

Hello guys, I have one problem and hope you'll help me to solve it...
I have current signal in range from 0-50 mA. However, I need to convert it to current signal 4-20 mA ( I have such instrument). I thought about linear transformation:
X (0-50) --> Y (4-20) and I get this equation:
y = (16/50)x + 4.
Is this possible to do with resistors?
Can you give me any advice, how would you do this?

Thanks!

 

[rdrast]

No, you cannot do it with resistors, unless you can figure a way to generate a 4ma current flow from 0ma.

Go to google, and type in 'Analog Signal Conditioners', and look at a few of the offerrings. One should do what you need.

 

[Tom Jenkins]

You may find a direct 0-50/4-20 mA signal conditioner, as rdast suggests. That is the best solution.

Failing that, you could run the current through a 200 Ohm resistor, and use the resulting 0-10 VDC signal as the input to a signal conditioner that converts 0-10 VDC to4-20 mA. This is a fairly common configuration.

 

[Pandiani]

So if I choose to run that current through 200 ohm resistor, I should connect resistor in paralel with current source (0-50 mA) and from that resistor (it's ends) I'm connecting to signal conditioner. Am I right?
Another idea is to use 0-10 V from resistor to circuit with Operational amplifier to convert to current signal, I heard it is possible, but no experience with this.
I think I'll try to get one signal conditioner
Thanks

 

[rdrast]

Here are some example signal converters:
http://www.miinet.com/products/sg_signal.shtml

 

[Tom Jenkins]

So if I choose to run that current through 200 ohm resistor, I should connect resistor in paralel with current source (0-50 mA) and from that resistor (it's ends) I'm connecting to signal conditioner. Am I right?
Another idea is to use 0-10 V from resistor to circuit with Operational amplifier to convert to current signal, I heard it is possible, but no experience with this.
I think I'll try to get one signal conditioner
Thanks

The resistor must be in series with the current signal. The input side of the signal conditioner must be in parallel with the resistor.

 

[rickboy25]

I agree with these guys, a signal conditioner would be the best,cheapest, and most simple solution. Here is a company that makes really superior signal conditioners at dencent prices.

www.prelectronics.com

These guys helped me out with a project I was working on last month and the 4116 from them is really hard to beat for any application for converting, isolation, temp, etc. It's a universal module.