Well Mike,  I thing you mean 4-20ma, BTW is very easy, you only need a
current source controlled by your 0-5 volt output, used this:
1 LM324
1 250 1% resistance.
1 resistence that depent of your main source.
1 2n2222.

I will tray to show you with a ASCII art, but I never do that:

                                                                    Vcc

|

|

>
                                                                       <


>

|
                                           1/4  LM324          |
                                                 |------ |           /
                   1-5V o------------ |  +      |       | /
                                    |--------|  -       | ---  |
2n2222
                                    |            |-------|       | \
                                    |
\
                                    |
|    E
                                    |
|
                                    |
+---------------------o

|
4-20ma
                                    |
                                    |---------------------
+---------------------o

|

|

>

<   250

>

|

|
                                                                     GND

as you can see I am very bad for this but I think you will be able to
understand. This circuit is usefull for 1-5V to 4-20 ma. you need do
some change for 0-5V to 4-20ma.



Montaigne, Mike escribis:

> The defacto standard input on Omega & other sensors seems to be
> 2-20ma with an internal impedance of about 1K.  Does anyone
> have a simple circuit to convert 0-5 volts from an PIC, or
> 0-10 volts from an external A-D on a PC which we are using now
> to this 2-20ma standard?  tks
>
> Mike Montaigne
> Atomic Energy of Canada Ltd.
> Station 18, Chalk River, Ontario
> K0J 1J0, Canada
>
> Phone (613) 584-3311 Ex. 4005
> Fax:     (613) 584-4040
> email:   montaignem@aecl.ca



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