Zero suppression and zero elevation are terms used in level measurement to adjust the measured level value to account for differences between the reference point (zero point) of the measurement instrument and the actual level measurement point. These adjustments are necessary to ensure accurate and precise level readings. Here's an explanation of each:

1. Zero Suppression:

   • Zero suppression refers to the adjustment of the measured level value downward (negative adjustment) to compensate for the offset between the reference point and the actual level measurement point.
   • In other words, zero suppression subtracts a certain value from the measured level reading to correct for the difference between the reference point and the liquid surface.
   • Zero suppression is typically used when the reference point of the level instrument is above the actual liquid surface, resulting in a positive displacement between the reference point and the measurement point.

2. Zero Elevation:

   • Zero elevation, on the other hand, refers to the adjustment of the measured level value upward (positive adjustment) to compensate for the offset between the reference point and the actual level measurement point.
   • In this case, zero elevation adds a certain value to the measured level reading to correct for the difference between the reference point and the liquid surface.
   • Zero elevation is used when the reference point of the level instrument is below the actual liquid surface, resulting in a negative displacement between the reference point and the measurement point.

Example:

• Let's say you have a level measurement instrument with its reference point (zero point) located 1 meter below the top of the tank. However, the liquid level in the tank is actually 0.5 meters below the top of the tank.
• In this scenario, you would apply a zero elevation adjustment of 0.5 meters to the measured level reading to correct for the difference between the reference point and the actual level measurement point.
• Similarly, if the reference point was located 1 meter above the liquid surface but the actual level measurement point was 0.5 meters above the reference point, you would apply a zero suppression adjustment of 0.5 meters to the measured level reading.

Zero suppression and zero elevation adjustments are crucial for ensuring accurate and reliable level measurements, particularly in applications where the reference point of the measurement instrument differs from the actual level measurement point. These adjustments help account for variations in installation, tank geometry, and instrument calibration to provide precise readings of the liquid level.