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Environmental conditions that can cause error 104, Hardware Relay Trip in the 55xxA series calibrators

While error 104 may be indicative of a repairable issue on the 5xxA calibrator family, environmental conditions can also cause the error.  These conditions are:
Inconsistent line power (either too high or too low).
Extremely low humidity
Improper grounding
If the power varies from the power setting currently selected here: mceclip0.png
And while the spec is 10%, getting even close to that variance may cause a problem. If power seems problematic, try using a very stable UPS.  
Check the lab's ambient humidity.  The recommendation is:mceclip4.png
To clarify a bit more what defines the low humidity limit, here is some adecdotal information:
40% is the low limit in the Fluke Primary lab
20% is the low limit in the Service lab, but according to the techs (who use the 55XXA calibrators most frequently) 35-40% is the best operating environment to avoid static.  
Improper grounding of the incoming power line is another source. Follow the grounding guidelines in the operator's manual:
Monitor line power and lab humidity when the trip occurs, and check grounding. 
If the problem persists, determine if a certain output setting or a certain model of Device Under Test ccauses the issue repeatably. Test more than one DUT model at more than one allowble setting.  If it seems to occur often and environmental issues or DUT issues have been ruled out, run a self test on your instrument.  
Record any error messages that occur and contact
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    Kevin Daily

    We have been getting frequent instances of this error lately on both of our Fluke 5522A units. We are having lab humidification issues so maybe this is our root cause. The published specs are for humidity less than a certain value. The stated possible condition is "Extremely low humidity". What humidity is too low?

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