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Alpha Meter Problems

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 I am working with an Eberline ESP2 (no laughing allowed) hooked up to a 43-68 and set up for alpha survey purposes.  On these alpha meters, usual range in a scan mode is from the highest measured value down to below 0.1 cpm (actually the lower end of the range is like down to 1E-6 cpm), as long as the survey is performed in a clean and fixed free area.  There is also a method of clearing out the last value so that when you start another scan, the meter will be in an expected range.  Today I got into a situation where I could not clear the display to get down into the expected range which should be <0.1cpm - 40 cpm.   I could eventually get the highest measured value in the range down to the expected, but the lower end of the ranging would not drop to the expected.   Now this wouldn't have bothered me quite so much for the surface measurement range, but if I was free airing the probe, the same problem was present.  It even had me going about getting a radon build up for a bit, until I realized that my ESP2/43-48 set up for beta was not reading alike.
Source checks showed it to be right where it should be.  BKG wasn't bad.  I took the probe apart and cleaned it as best as I could after visually verifying the Mylar was intact.  Air sample results had no activity outside of normal activity.
Do you have any idea what could be causing a problem like this?  Non-ionizing interactions?   Excessive personal magnetism?
Thanks for your attention.

check the mylar, if you can see through it you have the wrong mylar.  the double coated mylar must be used on these instruments to prevent light response

It's not the mylar.  We're using factory specific mylar and frames.  This happened to an instrument after it hs been used for the duration of the job.  It has been through source response cycles without a hitch.  Other instruments set up the same are not experiencing this.  I&C reports no problem with the set up. 
Obviously this is not an instrument response problem, i.e. the free air scenario.

Have you performed a Chi-Squared Test?

There is an obvious problem with your system and the meter should be placed out of service. Can it!

You will put too much energy into the topic and waste your time.

Have a Great Week,


Yea Moke is right, but i gave it the benefit of doubt.  time for rebuild or trash. just for grins-check to see if the mylar is transparent-you may have the right density but not the double coated.  seen it before-


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