> Well, we'd like to check that the blood samples we're storing actually 

> about this fact, urgently.


informed?  Would you trust a 20 quid meter from Maplin then?

> I'm guessing a temparature sensor that actually *works* at temparatures 
> that low is going to cost a tad more than your average room thermometer,

Not really, thermocouples are cheap (like a fiver) and measure down to 
below -100 degrees.

> but beyond that I don't see why it would need to cost more. It seems the 
> only reason for the higher price is that this is a critical device, so the 
> suppliers know they can charge the Earth and we will pay it. We have to.

Or the fact that there is a much lower chance it will break or mal-function. 
A simple example I can think of is that the connector where the thermal 
probe plugs in mal-functions somehow so that the electronics thinks that the 
temperature is -90 when really it is only -70.  Or some solder joint on the 
circuit board wasn't made completely correctly and messes up some other 
reading in an undetectable way once the temperature and humidity get to a 
certain value.  There are all sorts of failure mechanisms that needs to be 
checked and fixed somehow, and that costs lots of money.

> The mass spectrometers we have here all say "for research and development 
> only; not for diagnostic procedures" on them. I can't imagine why - it's a 
> mass spectrometer! Either it measures masses reliably, or it doesn't. If 
> it does, you can use it for anything you like. If it doesn't, it's a 
> worthless piece of equipment. So... why the sticker?!

Because they don't guarantee it will work reliably the whole time.  For them 
to guarantee that, they would need to do lots of expensive testing on every 
unit, probably design in lots of redundant systems, use more expensive 
components that have longer lifetimes, use better assembly methods etc.

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