Teledyne API Model 300M CO Analyzer Instruction Manual, 04033, Rev. A
3.2 Span Valve (Option)
If the span valve option is installed and a source of CO span gas from the cylinder
Pressing CALS switches the Sample/Cal valve and allows the analyzer to draw pressurized cylinder span gas through the pressure/span port (refer Figure
3.3 Zero/Span Valves (Option)
If the Zero/Span Valves option has been installed the operator can check the zero and span setpoints of the analyzer at any time by pressing the CALZ or CALS button. Refer Figure
Pressing CALZ switches the Sample/Cal valve and allows the analyzer to draw zero gas through the sample port. After a few minutes the CO reading should go to zero. If it doesn't, the operator may press the ZERO button followed by ENTR.
CALS works like CALZ except that externally supplied span gas is drawn through the analyzer. After a few minutes the CO reading should approach the span level. If it doesn't, the operator may press the SPAN button, followed by ENTR. The expected span gas concentration may be changed by pressing the CONC button.