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.
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.
> 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. <
>
> About the circuit, please give me your email, I will send it to you. <
could you please send me the info, thanks
bsu [at] huber.co.uk
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.
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.
> 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.
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I have done it on multiple job sites that were froogle. it is done with a simple resistor. if you are trying to save some $$$ it is not a difficult thing to do. However, you really need to worry about induction. (that has been my experience) if the client does not really know what there are asking, you should really try to sell him on the 4-20ma expansion model or a sending unit. If he/she refuses make sure in your contract you have a hold harmless clause, especially if you are doing this for a process control sequence.
>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
> 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?
no.you can not do it.
V=I*R V=4*250=1V OR V=20*250=5V
but I HAVE GOOD CIRCUIT FOR YOU.
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