wtw inoLab pH/Cond Level 1 Operating Manual page 68

Lists
Total dissolved
solids (TDS)
138
Mass that remains of the substances dissolved in an aque-
ous solution after a fixed filtering and drying procedure, as
far as these substances are not volatile under the conditions
of this procedure. The total dissolved solids refer to the vo-
lume of the filtered aqueous sample used und are given in
mg/l.