4 replies to this topic

[DracoRSA]

Hi, I am quite a newbie at electronics and specifically the Netduino. I would like some help on setting up the relevant circuit to allow me to do the following: I have a sensor that communicates on a range of 4mA to 20mA based on what it senses. I would like to monitor this reading with the Netduino. The sensor has two outputs used to connect an external monitor (Netduino) to it. A postive and negative analog connection. Could anybody help me with what I need in the circuit to connect this sensor to the Netduino? I would really appreciate some help

[bill.french]

Could you post a link to the specific sensor?

[DracoRSA]

Could you post a link to the specific sensor?

The product information can be found at Hanna Instruments

http://www.hannainst...8931A&id=017006

[bill.french]

Well I'm stumped. I don't think the netduino can measure current directly. You might need something like this that outputs varying voltage:

http://www.sparkfun.com/products/8883

[Jan Olof]

Well I'm stumped. I don't think the netduino can measure current directly. You might need something like this that outputs varying voltage:

http://www.sparkfun.com/products/8883

Thats overkill!
You only need a resistor. Calculated by Ohms law.
You need a voltage drop of 3.3 V at 20 mA, and then you just measure the volage over the resistor with the analog input of the Netduino.

165 Ohm at 20 mA gives a drop of 3,3V (max for the Neduino analog input) (U=R*I)

I would select the one closest below 165 Ohm I can find, with 1% accuracy I would take 162 Ohm.

/Jan Olof