A vacuum gauge is used to measure the pressure in a vacuum — which is further divided into two subcategories: high and low vacuum (and sometimes ultra-high vacuum). The applicable pressure range of many of the techniques used to measure vacuums have an overlap. Hence, by combining several different types of gauge, it is possible to measure system pressure continuously from 10 mbar down to 10-11 mbar.
Benson John Lossing, ed. The New Popular Educator (London, England: Cassell & Company Limited, 1891)