4-20ma Or 0-5v Voltage Or Current Which Is Better?

Just wondering,

In a sensing application - where a sensor is connected to reader or PLC etc.
What are the pros and cons over using Current output or Voltage Output?
I.e. the sensor is sending the signal, 4-20mA or a simple variable voltage.
I mean which has advantages over which etc.

Regards

Mark

A 4-20 mA signal has the benefit that you can tell the difference between a logical LOW signal, and a broken wire. If 4 mA is logic zero, then if the wire breaks you see 0 mA, which is easily detectable. Using a 0-5V voltage signal you cannot tell as easily, unless you define 5V as HIGH and e.g. 1V as LOW. Then a signal of 0V indicates broken wire.

// Mankku

4-20mA drivers have a much lower output impedance which makes them less susceptible to interference.

4-20mA is not affected by the resistance of long wire runs as long as the output has enough compliance. For short runs voltage output is easier since 4-20 is normally converted to a voltage for measurement.

From all you responses it looks that a 4-20mA output has far more benefits then the voltage output.

So does anyone know why you get sensors with voltage output only? Are they cheaper to make or are they more linear or accurate? Why on earth would you use a Voltage output instead of a 4-20mA version?

voltage based can be paralleled easily. if you parallel current sources, you might get 2-10mA, or 1-5mA and 3-15mA depending on the sharing.

and with 1-5mA you might see an issue where 4mA is read as -1PU and 2mA is read as an open and shows up as 0PU. this kind of jump can be bad.

4-20mA drivers should have a very high output impedance, and the receivers should have a very low input impedance.

More benefits for Certain situations, not most/all.
Voltage output is very easy to deal with. Personally I would use voltage type if the benefits of current type aren't required.

Couldn't this be overcome by adding a resistor in series with each sensor (as when paralleling LEDs, BJTs, etc.)?