HED Faults - causes and prevention?

Good Morning/Afternoon/Evening,


I have seen several instruments obtainined a HED error/fault during sequencing or during the tuning process. These instruments have been in various cuontries with varying electrical output, but all protected by high spec. UPS systems.


Occasionally the HED fault disappears for a while and functions normally then reappears agian maybe a month or two down the line. The HED volts are fine and below 1500 V (with a limit of 2500 V).

What causes these faults to occur?


I have also seen HED faults occur and the only way to fix them is to replace the HED power supply located in the MS circuit board case. We have tried changing the horns first but the issue was still there until the power block was replaced.


Again what are the causes for this issue? As we don't know why this is happening so we don't know how to prevent it.

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  • In the attached email to the thread, it talks about power requirements. This can be presented to the electrician.


    Please contact the manufacturer of the UPS or other isolation device if you wish to use these to supply power to Agilent Technologies GC or GC-MS system. Inform the isolation device manufacturer of the varying cycle-by-cycle load behavior of the Agilent system to obtain a recommendation from the manufacturer for the proper size, capacity, and type of UPS or other isolation device.

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