100cm2

[mostlyharmless]

Where did the standard of 100cm2 come from and how long have we been using it?

[X-Nuke]

Well, at the risk of showing how little I know, I'll go with it being roughly equal to the size of a dollar bill (and makes the math easier too) and in use since the 1940s.

Bill

[Motown homey]

I remember that they told me in ELT "C" school that there were three criteria: 1) It's easy to do - two fingers on a smear dragged 16 to 18 inches (usually in an "S" pattern).  2) Dragging a filter paper smear much further tends to deteriorate the smear and you start to lose sample.  3) It's a nice round number.

[Adam Grundleger]

If I remember correctly, in ELT school they taught us it was large enough for a representative sample but small enough that the swipe would not come apart.  I wouldn't doubt the round number is for radcon math.  The limits are also written to 100sqcm, though I'm sure that's based on the sample size. 

[SloGlo]

bean a factor of tenn, it makes alla math sew much easier.  peek oh curies work best two.  gist axe enny buddy dat went threw oral boards.   

[HydroDave63]

There once was a time before 100cm²...



Saw one of these for sale on eBay last month, the venerable old AN/PDR-10A

[SloGlo]

Saw one of these for sale on eBay last month, the venerable old AN/PDR-10A

'n shorely won of da shortest usage times for a military radiac instrument....
mebbe 150cm² area corfuzt two manny peepul?

[HydroDave63]

'n shorely won of da shortest usage times for a military radiac instrument....
mebbe 150cm² area corfuzt two manny peepul?

in those days, 4"x6" photos were still common, and a 4x6 is darn close to 150cm²

100cm² is ~ 3"x5" , which has been common as well, any coincidence? 

[SloGlo]

in those days, 4"x6" photos were still common, and a 4x6 is darn close to 150cm²

100cm² is darn near 3"x5" , which has been common as well, any coincidence? 

no wing hour gubbermint prefurs a thousand words over a worthy picture, eye wood say..... no.