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4-20ma to 0-10 volt conversion

Discussion in 'Electronic Basics' started by [email protected], Mar 21, 2007.

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  1. Guest

    Does anyone know of a single ic that will take a 4-20ma signal and
    convert it to a 0-10 volt signal ???

    It looks like someone would produce such a beast by now....but my
    google searches have turned up nothing.

  2. Tom Biasi

    Tom Biasi Guest

    Can you settle for 2 to 10 Volts?
  3. Yes, a 500 ohm resistor. Add a 2 volt battery and you have 0-8 volts. A 625
    ohm resistor and a 2.5 volt battery (or offset) gives you 0-10 VDC.

    Usually a 4-20 mA signal is a control loop which allows transducers to take
    their power from the loop supply, and change the current according to what
    they measure. The display can be as simple as an analog meter with the
    pointer offset below the zero point, or can be an electronic digital
    display powered from the loop. Power can come from any device in the loop,
    or a separate battery or supply.

  4. Jamie

    Jamie Guest

    you just use a voltage network to feed the transmitter from converter.
    with this network, you can use an Op-amp with dual rail supply or
    some negative offset to give you 0 volts at 4 ma's
    something like a 24 DC supply using a 100 ohm Resistor to supply
    the transmitter. The op-amp simply uses both inputs to monitor the
    offset of the voltage on this resistor, which will translate to a
    voltage output..
  5. A 1/2W 500 Ohm resistor will give you a 2V to 10V signal. You can use a
    smaller resistor and an op-amp to not place so much load on the line.
    Outside of using a resistor, you could measure the magnetic field coming off
    the wire, but that's getting out there.

    If you have to have 0-10V, you could do it something like this and use
    another op-amp to double the voltage output:
  6. Chris

    Chris Guest

    An operational amplifier is versatile and capable of performing the
    conversion. Assuming you have a single 15V supply, here's an LM324-
    based circuit that will do the job fairly well (view in fixed font or M
    $ Notepad):

    | VCC
    | +
    | |
    | .-.
    | 12K| |
    | | |
    | '-' VCC
    | | +
    | .-. |\| Set For Vo = 0V
    | 1K| |<-------|+\ at I(in) = 4mA
    | | | | >-o--------.(1V)
    | '-' .---|-/ | |
    | | | |/| | | ___
    | === | GND | | .---|___|---.
    | GND | | | | 25.5K |
    | '--------' | | |
    | | ___ | |\ |
    | + |\ '---|___|-o---|-\ |
    | o----o-------|+\ ___ 10.2K | >----o---o Vo
    |I(in) | | >-o--|___|-o-------------|+/
    | .-. .---|-/ | 10.2K | |/
    | 249| | | |/ | .-.
    | | | | | 25.5K| |
    | '-' | | | |
    | - | '--------' '-'
    | o----o |
    | | ===
    | === GND
    | GND
    (created by AACircuit v1.28.6 beta 04/19/05

    The 249 ohm terminating resistor for your current loop will produce a
    1 to 5 V input at the first op amp. The second op amp is supposed to
    produce a 1.0V reference to subtract from the 1-5V. The resistors on
    the third op amp are set up to provide a gain of 2.5 for the
    difference -- 0-4V becomes 0-10V.

    These are standard 1% resistor values. If you need/want 5%
    components, try using 30K and 12K in place of the 10.2K and 25.5K. If
    you need more accuracy, you might want to replace the LM324 with a
    lower drift single supply quad op amp, and use a voltage reference
    instead of your power supply to create the subtracting 1V.

    Good luck
  7. jasen

    jasen Guest

    If you can live with a 2-10V output the "chip" is called a 500 ohm resistor
    (2 1K resistors in parallel)

    if that's not suitable something can probably be done using an op-amp.

  8. MassiveProng

    MassiveProng Guest

    There is 4 to 20mA NON-LINEAR range for instrumentation. There is
    4 to 20mA LINEAR range for instrumentation.

    Our IR thermometers offered 0 to 1 volt conversion as an option, but
    I do not recall 0 to 10V.
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