The following definitions will help to ensure proper use of the data contained in this section.

1. ZERO (Level-Tek or Level-Lance, On-Off) — This is the "set point", the point where the desired actuation is to occur.
   
   
2. DIFFERENTIAL (Level-Tek or Level-Lance, On-Off) — This is the distance, in pico-farads or inches or feet, from ZERO to the point at which “reset” is to occur. Sometimes referred to as “Pump ON to Pump OFF.”  

   NOTE: All instruments do not have 100% differential, i.e. 314B has only a 50% differential adjustment. Ensure that the differential required is within the capabilities of the instrument selected.

3. ZERO (Level-Tel or Level-Lance, Continuous) — The 0% level point on the sensing probe.
   
   
4. 100% (Level-Tel or Level-Lance, Continuous) — The FULL level point on the sensing probe.
   
   
5. SPAN (Level-Tel or Level-Lance, Continuous) — The distance in pico-farads from the ZERO level point to the FULL level point (100%).
   
   
6. TERMINAL CAPACITANCE — The MINIMUM amount of capacitance present when NO product is present in the vessel.
    
   This is:
   1. The capacitance of the probe gland (and sheath and cooling extension, if used) PLUS
   2. The capacitance of the coaxial or triaxial cable when remote mounting an instrument (not applicable for models 158A and 310) PLUS
   3. The capacitance generated between the probe and the vessel with AIR as the dielectric. In other words, the absolute minimum value of capacitance generated in that particular probe/vessel installation.

      NOTE: Sheath capacitance is the same pF/ft. as gain of probe. Cooling extensions are 4 pF for each 4” of extension. Standard coaxial cable capacitance is 13.5 pF/ft. Low noise coaxial cable is 21.5 pF/ft. Triaxial cable capacitance is 17 pF/ft.

7. TERMINAL/SPAN RATIO — The “terminal” capacitance divided by the “span” capacitance. This ratio must not be exceeded where specified on product specification sheets (all instruments do not have this restriction).
   
   
8. TERMINAL ADJUSTMENT/ZERO ADJUSTMENT RANGE/MAXIMUM ZERO
   SUPPRESSION — This is the maximum “zero suppression” of the capacitance value at the zero point level in the vessel. This value cannot be exceeded.
   
   
9. CAPACITANCE CHANGE — The amount of capacitance difference between ZERO and 100% points in Level-Tel or continuous Level-Lance systems; the amount of capacitance difference between product and no product in point level (Level-Tek/Level-Lance with no Differential) applications; or the amount of capacitance difference between ZERO & DIFFERENTIAL points in Level-Tek/Level-Lance applications utilizing Differential.
   
   
10. TOTAL CAPACITANCE — The total capacitance value (not capacitance change) with tank or vessel at the 100% level (includes terminal capacitance).

    NOTE: The pF/ft. minimum and maximum span of the instrument selected must be met. Ensure that enough capacitance change is generated to meet the minimum span requirements and that it does not exceed the maximum span of the instrument.