The dreaded and often misunderstood "EXCESSIVE SIGNAL LEVEL" error message strikes fear in the hearts of Spectroscopists and technicians alike. Typically this error indicates that the mass spectrometer is responding to a signal or sample that is causing the electronics to go into a saturation or signal overload condition. There can be several causes for this error.

1. Vacuum Problems
2. A Dirty Ion Source
3. Recently Cleaned Source
4. Excessively Concentrated Sample
5. Bad Electron Multiplier
6. Defective Electronics

About 90% of the time the solutions are simple and can be corrected quickly.

Vacuum Problem - Poor vacuum can cause a number of problems for mass spec systems. Checking your operating vacuum should be a routine procedure even when problems don't exist. It should also be one of the first things considered when a problem occurs. Bad vacuum can cause an EXCESSIVE SIGNAL LEVEL error by causing the electron multiplier voltage to rise to excessively high voltage levels in an attempt to reach target tune values during auto-tune. Additionally a user may have raised the multiplier voltage manually in an attempt to compensate for lost sensitivity resulting from a bad vacuum condition. The high voltage can result in some ions saturating or overloading the detector electronics.

A Dirty Ion Source - When the source gets dirty it becomes less efficient at doing its job of producing ions that pass through the mass filter to the multiplier/detector. When performing an analysis, the operator may try to compensate by increasing the multiplier voltage. When performing an auto-tune, the software may raise the multiplier voltage in an attempt to achieve proper target abundances. Both of these scenarios can cause the multiplier to go into a saturated or overload condition and cause the EXCESSIVE SIGNAL LEVEL error. WHEN IN DOUBT, CLEAN THE SOURCE but be careful not to further dirty or contaminate the source as it is being cleaned. Also, after cleaning, DO NOT BAKE THE SOURCE PARTS IN THE OVEN. This will cause oxidation on the metal source parts and open up a whole host of other problems.

A Recently Cleaned Source - It is inevitable that your source will become dirty with continued use. As this happens the multiplier voltage will increase when the software tries to achieve target abundances as sensitivity is loss. When you install a recently cleaned source, it will be necessary to either manually decrease the multiplier voltage or reset the tune values to the original default values.

An Excessively Concentrated Sample - If the EXCESSIVE SIGNAL LEVEL error appears during sample analysis yet the system tunes and scans perfectly, the cause is most likely an excessively concentrated sample or sample constituent. There are two ways around this issue. The first would be to manually lower the multiplier voltage prior to the start of the run. This is assuming that the other constituents in the sample can be maintained at the proper detection level and you're not dealing with a previously run calibration curve. The second would be to dilute and re-analyze the sample.

A Bad Electron Multiplier - A bad multiplier, whether it is old or new can cause the EXCESSIVE SIGNAL LEVEL error. An old multiplier can cause the software to drive the multiplier voltage to excessively high levels in order to compensate for the loss in sensitivity. This in turn causes the detection circuitry to go into saturation or signal overload. A new multiplier could be manufactured ‘extremely hot' which means it has an excessively high gain at relatively low voltages and causes saturation in the detector circuitry.

Defective Electronics - After you've logically and methodically eliminated all the other possibilities the final possibility is that an electronic board has malfunctioned. A power supply that has decided to take a permanent vacation to the Bahamas or a leaky capacitor that has decided that it's time was up, can cause this error. For this scenario, please contact Alpha Omega Technologies' World Class Technical service department for assistance.