Electronics > Projects, Designs, and Technical Stuff
Transimpedance converter / amplifier
(1/1)
ACertainIdioticEngineer:
Hi first post here in this forum, sorry if this already existed on the forum, didn't find any tho.
Currently trying to "design" a circuit which can convert a 4 - 20 mA sensor into a voltage which i then can read out with the Arduino. The problem lies in how precise it has to be. The resolution of the laser is 0,2 mA/mm in 16um steps. So this circuit should just convert the current of a 16um step into 4,88mV while being stable enought that the ADC doesn't change the LSB when on the same point. The Circuit i built should work however when i meassure the virtual ground on the OPAmp I get a voltage of -12V and the current to the sensor is -1,7mA. The Sensor can drive up to 300 \$\Omega\$ and if i meassure the laser without the OPAmp it works just fine. The 1k \$\Omega\$ resistor represents the next load for an inverting OPAmp. The pins should be connected correctly since i rebuild it 3 times and got the same error each time. Powering it from an external 12V power supply (~13,4VDC). The Laser is a Z4M-W100RA
KT88:
The Z4M-W100RA features a current source and the TIA inverts the voltage. This circiut would require a negative supply and another inverer to get a positive output for your Arduino...
You could use just an appropriate shunt that feeds directly into the Arduino. Maybe a buffer witht the possibility to cancel the 4mA related offset. Some overvoltage protection won't be bad as well.
ACertainIdioticEngineer:
thanks will try it out... forgeting the negativew supply rail... :palm:
Navigation
[0] Message Index
Go to full version