How to output analog current more than 2mA

[cli21]

Hi johnsold,

The device is made by myself, it can be considered as a resistor. Actually, I tried using a resistor(100Ohm), then the voltage of the resistor can't exceed 0.23V.

Thanks.

CJL

[johnsold]

0.23 V/100 ohms = 2.3 mA = limit for AO.

Lynn

[cli21]

Yes. So it seems protection diode is working. I have suspected that,too. But I think there should be a way to solve this problem. 

CJL

[Henrik_Volkers]

Did you connect the powersupply GND ?

[cli21]

Hi Henrik,

My power supply is a DC power supply which doesn't have GND. So I designed a circuit to split the voltage and construct a virtual ground. But I need some compenents such as copacitors which I don't have right now. I plan to get these components and try your method tomorrow. 

Thanks,

CJL

[johnsold]

Even two equal value resistors to create a 'pseudo'ground might be enough to eliminate the diode issue. Try two 1000 ohm resistors in series from +15 V to -15 V and connect the DAC ground to the junction of the two resistors.

Both systems, the DAQ and the controlled device, MUST use the same common reference or ground. If your device is floating, the impedance of the voltage divider I described above may not matter.

Lynn