10V Analog Output Voltage

This application note explains how to obtain a 0 to 10V analog output voltage using the EMANT300. This circuit is used in a proportional valve application. The proportional valve control flow rates from 1.4 to 5m3/h. The variable opening of the cross section is changed proportional to the 0-10V input signal

The analog input range required by the proportional valve is 0 to 10V whereas the analog output of the EMANT300 USB DAQ module is a current from 0 to 1mA (see EMANT300 specs).

The following circuit is used to convert the 0 to 1mA output to 0 to 10V output.

The opamp LM2904 is connected in a negative feedback configuration. V- is given by

IDAC is the current output of the EMANT300. V+ is given by


In negative feedback, you can assume that V+ = V- Combining both equations gives

Substituting the component values from the schematic into the equation, gives the following relationship


Note:

  1. The supply voltage to the opamp should not exceed 32V for the LM2904.
  2. The resistors used should be 1% or better.

C# code

using System;
using System.Collections.Generic;
using System.Text;
using Emant;

namespace Vout
{
    class Vout
    {
        static void Main(string[] args)
        {

            double volt;
            string input;

            Console.WriteLine("Output Voltage 0 - 10");
            input = Console.ReadLine();
            volt = Convert.ToDouble(input);

            Emant300 DAQ = new Emant300();
            DAQ.Open();
            // 10V requires 1mA output current
            DAQ.WriteAnalog(volt/10);
            DAQ.Close();
        }
    }
}