How To Choose Between Single-Ended or Differential Voltage Measurement | Differential Featured | Industry Technology Paper

How To Choose Between Single-Ended or Differential Voltage Measurement | Differential Featured | Industry Technology Paper

Learn How to Choose Which Method to Apply

Examining important aspects of single-ended and differential voltage measurement, along with tips on why it might be better to choose one method over the other.

Voltage is a difference in electric potential between two points and is a measure of the force for current flow in a conductor or circuit.  You can choose to measure voltage single-ended, or you can measure voltage deferentially.

The differential input offers more freedom when connecting to earth grounded or non-grounded (isolated) signal sources than the single-ended input, because its signal connections may be offset and separate from signal return, which may or may not also connect to earth ground.  However, an earth ground path to return must still be made, and you should be careful not to provide more than one earth ground connection to return to avoid creating a ground loop circuit that could offset or interfere with your measurement.

Beware of Ground Loops

Because differential inputs can also connect to earth grounded source signals, you need to be aware of your instrument and determine if its Return connection is also connected to earth ground in order to avoid situations where two separate connections to earth ground may create a ground loop, which can lead to measurement error and equipment failure.

Instrument instructions will normally tell you to limit yourself to one earth ground connection in a circuit in an effort to avoid generating a ground loop which can interfere with your measurement, but this is really only required when the earth grounds are at different potentials which would push error current between them (not likely for closely spaced I/O).  Be aware of where your output and input connect to earth ground—if they each connect separately to earth, how far apart are their connections to earth?  If the distance between the output and the input is larger than about 3 meters, or the distance between the earth grounding points is long, you may have to introduce an isolation barrier between the signal source and measurement device.  The presence of isolation between the output and input circuits will “break the ground loop” by allowing the earth grounds of each circuit on each side of the barrier to be at different potentials (within the limits of the isolation rating).

See Acromag’s transmitter options.

Use the download document button get get the full How To Choose Between Single-Ended or Differential Voltage Measurement | Differential Featured | Industry Technology Paper