Hi!
I'm currently working on a development project at work where I have a DC current of between 0mA and about 0,5mA depending on the temperature. (Making a integrated thermocouple). The principle is working and I can read a steady current with a multimeter. Now its time ro design a curcuit that initially may get the data till an Arduino.

My current idea is to have an current OP-amp with a gain of 1000 to get THE interval up to 0-500mA.
Then get the current into a BJT where I put 5V that from the emitter could be read by the arduino.

Because im pretty new in the electronics Im asking if this is a good idea or if there is any better solutions. And what components that would suit.

Thankfull for feedback!
//Oliver

 

hi Oliver,
Have you considered passing the 0mA thru 0.5mA current thru a high value resistor and amplifying the voltage across the resistor with a high input impedance OPA.
What exactly is the current source.
Eric

EDIT:
This would be an option. Vout to the Arduino ADC input.

 

hi Oliver,
Have you considered passing the 0mA thru 0.5mA current thru a high value resistor and amplifying the voltage across the resistor with a high input impedance OPA.
What exactly is the current source.
Eric

EDIT:
This would be an option. Vout to the Arduino ADC input.

No I haven't bit that seems to be a simpler solution! Thank you very much! I will implement this to the project!

 

hi O,
What is the current source, it would help if we knew its output impedance.
E

 

hi O,
What is the current source, it would help if we knew its output impedance.
E

I will try to explain.
I have constructed a thermocouple which consists of ni-wire x cu-wire x ni-wire. When there is a differential in temperature between the junctions of the ni-wire and cu-wire (x) results in a small output voltage. One of the nodes is located on a AC circuit which led to a problem with measuring the voltage because ofta THE multimeter having a loser resistance then the AC circuit. It is possible tog measure the current of the Wire. I hope it makes Sense to you. I Will