Alberta Boilers Safety Association (ABSA) Practice Test

Transmitters typically convert physical quantities associated with processes, such as temperature, pressure, or flow, into a signal that can be transmitted to control systems or monitoring equipment. In this context, the 4-20 mA signal is widely used and recognized as a standard in industrial automation and process control.

The reason 4-20 mA is the correct choice is that it represents an analog current loop signal, which has several advantages in industrial applications. Operating within this range allows for a clear distinction between the lower and upper limits of measurement. The 4 mA level indicates the lowest value of the measurable physical quantity, while the 20 mA level indicates the highest. This range is particularly beneficial because it allows for power supply and communication reliability, even when the signal experiences some degradation due to distance or other factors. Additionally, a current signal can travel over long distances without losing integrity, making it ideal for transmitting data in various industrial settings.

In contrast, the other options represent either specific pressure values (0-25 kPa, 0-185 kPa) or a digital signal. While the digital signal is suitable for certain types of communication, it does not provide the same continuous range or the ability to easily represent varying levels of measurement as