circuit design

[vems]

hi,
I am doing an electronic project with microcontroller.Here i am reading the flow rate with flow meter which gives 4-20ma.I need a circuit to convert 4-20ma to 0-5volts analog voltage to 0-5volts digital voltage . so that it can be given as input to the microcontroller(89c51rd2).Please help me,so that i can proceed my project

 

[bmcculla]

What you need is a simple opamp circuit. Look up "non-inverting opamp" on google.

**broken link removed**
Has some good info.

Brent

 

[stevez]

Do you want 0 to 5 volts or 1 to 5 volts? The guys who did control work for me used a resistor of the correct value (250 ohms) to yeild a voltage drop of 1 to 5 volts with a current flowing of 4 to 20 ma. We used to avoid spanning to zero because zero is pretty small. That only gets you part of the way there.

 

[jbeng]

I agree w/stevez to use a 250 ohm resistor across your 4-20 loop to
get 1-5VDC. 1VDC=no flow and 5VDC=max flow. Then use an A/D
converter from there to get a digital representation of your flowrate
data into your micro ...