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0-20mA/0-5V Receiver

Siyavash Asadi
Intellectual 665 points
Other Parts Discussed in Thread: RCV420, INA198

Hi, I need a high precision current loop receiver, I used RCV420 , it is ok but it need high voltage 15volt dual supply, I need IC with 8<power supply<10, my application is reading 2 wire pressure sensor. one is 0 volt and other is VCC and also current output signal.

Any help would be greatly appreciated.

 

  • 0
    TI__Guru 62035 points

    Hi Siyavash,

    You can make a high precision 4-20mA receiver using a rail-to-rail input op-amp and a shunt resistor as shown in some posts such a the one shown here:

    http://e2e.ti.com/support/amplifiers/precision_amplifiers/f/14/p/242351/850461.aspx#850461

    Could you provide more information regarding what you're trying to build?  Does the receiver circuit you're building derive power from the 4-20mA loop, or is there a separate 8-10V supply?

  • 0 in reply to Collin Wells
    Intellectual 665 points

    Hi Collin Wells,

    thank you for your reply.

    Excuse me I had some mistake in my first post. now I say what I need.

    I want to read pressure sensor. it is a 2 wire. one wire is ground and second wire is power and also signal. it is 4-20mA. the pressure sensor work with more than 8 volt. my request changed, now I just want a precision current sensing solution and power supply is not important.

    now I got I can't use RCV420 with Basic connections like figure.1 in it's data sheet, I think problem is signal and power are in same wire. I found Figure.15 . I tested it, it worked without any problem but if I want use RCV420 with this circuit I prefer to use Current Shunt Monitors like INA198 because it doesn't need high and dual supply.

    Current shunt monitor with shunt resistor has problem, because we need very accurate resistor for having accurate measurement. 

  • 0 in reply to Siyavash Asadi
    TI__Guru 62035 points

    Hello,

    There really aren't any other options besides the RCV420 which have the integrated shunt resistor required for the 4-20mA receiver. Other solutions, including the INA198, will require an external shunt resistor as shown in my first reply. 

  • 0
    Intellectual 310 points

    Hi Siyavash,

    I guess the connection you've made for your sensor with the controller (or an amplifier) might be wrong.

    (I use the word "controller" in comparison with industrial standard).

    Normally for a 4~20mA with 2-wire interface, the connection is as follows:

    "PLUS" terminal from the controller (it can be a voltage source of 24VDC in case of an amplifier) is directly connected to "PLUS" terminal of the sensor. "MINUS" of the sensor is connected to input of the amplifier, not the "GROUND".  In other words, the sensor must be connected in series with connection between +24VDC and input of amplifier.

    As Collin mentioned, there should be a shunt resistor between this input at amplifier and "GROUND". Please note that the shunt resistor must be connected at the input of amplifier as close as possible (For high-precision). The voltage present at the input of amplifier will be equal to 'I_in * R_shunt '. You can choose any resistor to get a desired voltage range.

    Needless to say, you will have to use high-precision (0.1% or better) for the best result. I was working in industrial automation field, and this was a common matter there. We used to connect the sensor to a controller, which already has an amplifier built-in.

    Regards,

    Binoy Raphael.