External or in-line amplifiers are available for all types of load and pressure sensors and are valuable when an amplified signal is needed but the conditions do not allow an internal amplifier to be used.
Miniature load cells or pressure sensors often do not have room for an internal amplifier.
Also, internal amplifiers can be damaged if the sensor is to be used in an application where the temperature exceeds 300° F.
In those cases, the amplifier can be located away from the sensor in an area with a more hospitable ambient temperature.