Digital pressure gauges for partial pressure blending are highly accurate and quite expensive. Most types are battery powered. During the offseason, if batteries are not removed, they can rupture and leak acid into the gauge thereby destroying it. This can be a very expensive lesson. Global's digital mixing gauge #45305OX can now be purchased with an external power supply eliminating the need for batteries. Option only, does not include gauge. This option must be ordered with the #45316OX external battery pack.