Let me get your answer:
You want to build a transmitter, that consumes between 4 and 20 mA
Then I don't get it. When you say transmitter, you mean a wireless data transmitter, or something else?
If you want to have a linear output current, depending on 0-5V input, just put a resistor in series (between the output of the system and the input of the next stage).
to change 0-5 volt to 4-20ma loop current. most that i have seen use op-amps their are many plug in mods to do this with some have switch programable for input to output combinations and different powering as 12 vdc to 120 ac. So what are you trying to do?
1. I want to use DAC which is unipolar rather than bipolar to achieve this.
2. The circuit should be able to convert this transducer reading to proportionate 4-20 ma current loop ( of course after calibration )
What kind of accuracy is required ?
(if this is a car fuel monitor then the sensor may not be that good anyway --- +/-10% ???)
Does the output current have to use the zero volt rail as one of the output terminals ?
(if you are driving a moving coil meter then the output could be independent of 0v ?)
let me suggest that if you are building one from scratch to use a pulsed out put device a (optical encoder) with quad out so you can count backwards. Take this pulse train direct into a processor from start x amount of pulses are one flow unit x amount of units is total amount, measured over a time frame 60 minutes, seconds gives you flow rate....you would have to write a program too....i have done this once with a embedded processor for a control system. It had a screen display that you could make it show info in numbers or graphics.
joe
Idea it to convert pulses received from a tranducer which is installed in flow to a calibrated 4-20 ma output. I am trying to measure flow between 40 to 100 litres per minute and send this information over 4-20 ma current loop to a controller.
Pink Panter
I guess you can use an IC that does the job you want.
Or check national semiconductor for a design they have in the site about 4 - 20 ma. transmitter, this is done by a diff opamp.
the circuit in your posting will work if your transducer has 8 bit output if it is only a 0-5 square wave pluse train output it won't. what is the transducer make model ect ... maybe i don't understand what signal you are starting with.
joe