Calibration Types: Zero vs. Span
The ULTIMA X5000 has two types of calibration: Zero and Span calibration.
Zero Calibration resets the baseline level reading to zero. If the target gas is suspected to be occasionally present, it is best to also use a zero gas cylinder during the zero calibration. If the target gas is not present in the atmosphere, an additional calibration cylinder is not required.
The "Calibrate" option involves first applying a zero gas followed by the span gas. The span gas is a known concentration of gas which adjusts the accuracy and precision of the transmitter to the known value; this is referred to as the “Span Value. See Figure 41 .
The Sensor Span Value in the device menu should be the same as the concentration listed on the calibration gas cylinder; unless an LEL simulant gas is being used.
The XIR PLUS sensor can be calibrated to a wide variety of gas compounds using either 0.1 % Propane, 0.6 % Propane, or 2.5 % Methane and MSA's gas table. See Table 21 for a complete list of gas compounds and corresponding tables and span values.