"Mark Cooper" wrote in message
.. .
I picked up a floating hydrometer and I'm wodering if they are affected by
barometric pressure? When I float it in RO water it reads 1.004. Since I'm
located in Iowa, which is above sea level a bit, will this affect the
reading a bit?


Nope. A hydrometer measures the specific gravity of a liquid independently
of barometric pressure. However, hydrometers are effected by the
temperature of the liquid you are measuring.

You need to adjust for temperature.




As it is, I use 1.004 as a base reading and adjust accordingly.




Thanks,
Mark