[Halld-tracking-hw] clean room and particle meters

[Curtis A. Meyer]

  Hi Everyone -

   the particle meter that we (finally) received is a Hal Technology
HAL-HPC300 meter. It also has a USB connection and can be read
out by a PC running a pre-windows-7 operating system into an excel
file. It cost about $1800 and measures the number of particles in the
following ranges:

0.3 micron and larger
0.5 micron and larger <== standard clean room rating
5.0 micron and larger

    We also got together with our EH&S person (Jeff) who also has a 
particle meter.
His was last calibrated in May. We ran them side-by-side and our's was 
consistently
larger. He felt that ours was probably more accurate as it was new.

    Jeff also told us that a single measurement is pretty much meaningless.
For him to rate a room, he measures it 3 times per day for a week and
averages. He has also seen VERY LARGE day-to-day swings based on
weather, rain, etc....

   Based on this information, we will continue recording our readings 
daily in five
locations in our clean room. We will then produce weekly and monthly 
averages.
This probably means that the weekly averages will track the rating of 
room, and
we can use those to watch for drifts in the room.

    Finally, Jeff felt that if he had made a measurement in a dirty area, it took a while
for his meter to come back to normal. He said that the meters are made to measure
clean rooms (not dirty ones). Based on this, we are now planning to leave our meter
in the cleanroom.

     Curtis
-- 
Prof. Curtis A. Meyer		Department of Physics
Phone:	(412) 268-2745		Carnegie Mellon University
Fax:	(412) 681-0648		Pittsburgh PA 15213-3890
cmeyer at ernest.phys.cmu.edu	http://www.curtismeyer.com/