There is a statement in the manual that says the system alarm is activated if the span parameter is out of limits. What exactly does that mean?
The span parameter is out of its limits when there is not enough slope adjustment to complete the span calculations. This is a software function where a span factor is used to multiply the A to D signal, this is indicated as slopes. An example is the result of maybe attempting to span with a zero gas, it will just continue to re-calculate the slope until it runs out and then turn on the system alarm. The system alarm will activate under any of these conditions listed in the manual. Ref section 3.3.4. This includes when self test fails, as you reported is the case in this instance. Turn the instrument off, and when turned back on, bypass the self diagnostics, and the unbalanced cell failure will alarm will not activate. Or you can perform the self diagnostics with air in both sample and reference side of the cell. The solution is to change the condition which caused the failure, and then reset the alarm.
