Re: Poor P/Button Switch Contacts ESP-2

["Mike Malaxos" <rss@arach.net.au>]

Hello All,
	
	I have a couple of questions that I hope someone out their is willing to
comment on.

1	Has anyone had trouble with push button contacts on an Eberline ESP-2.
	
	Contact is made across two printed circuit tracks by a ?? conductive
button about 3 mm 	diameter connect to a flexible apron. Cleaning the
tracks and button surfaces did not seem to 	make a permanent difference. It
is time consuming removing the circuit boards to access the 	switch
surfaces so I want to get it right at the next attempt.

2	I am using a 40 mm active diameter thin window LND 7313 GM detector
counting for 600 	seconds.

	Efficiency using a calibrated Sr 90 Y90 source indicates a 4 Pi  efficiecy
of	around 20%. 	Background is around 25 cpm. What MDA for Cs 137 using the
Beta and a confidence of
 	level of 2 std and 3 std (97%) is usually quoted by those with similar
systems and accepted as 	being reasonable in practice. The wipe dirty side
up is enclosed in a very thin plastic bag in 	contact with the input
screen.(say wipe input window < 1.5 mm). 

3	Repeat of the above question only this time we are using a Johnson 50 mm
alpha probe 
	Background is around 1 cpm . Am241 wipe is 1mm from input screen.
Threshold is set below 
	Am241 Alpha.   
	

Thanks in advance.
----------
>Best Regards
M.Malaxos
Radiation Safety Services
Fax 61 294 1533
email rss@arach.net.au