30 Hg

[220 maple]

I have looked at least one picture posted by a producer using 3/16 tubing of their vacuum gauge reading almost 30Hg, I believe there are others that claim they are pulling 30 Hg? Is not 30 Hg perfect vacuum that can only be achieved at sea level? Just Curious?

Mark 220 Maple

[maple flats]

Yes, but likely a gauge we (maple producers) use is not scientific grade and thus is less than 100% accurate. But, then it might be real close and get 30" on locations at lower elevations and during times of high barometric pressure. While std. air pressure at sea level is 29.92",the high and lows are a rather wide range, for just considering it it related to the weight of the thin air overhead.

[DrTimPerkins]

Yes, but likely a gauge we (maple producers) use is not scientific grade and thus is less than 100% accurate.

Standard vacuum gauges used in the maple industry are either +/- 2% or even +/- 3% full-scale, so if the actual (true) value was 29" Hg, you could see anywhere from about 28-30" Hg on the dial and still be within the specs of the gauge.