1. A welding monitor for connection to welding parameter sensing means, the monitor comprising storage means for storing at least two sets of predetermined acceptable ranges for one or more welding parameters; comparison means adapted to compare an operating value of said the or each parameter, determined by said sensing means, with said corresponding at least one range; and display means for displaying information relating to said stored ranges and operating values and responsive to said comparison means to indicate the relationship between an operating value of at least one of said parameters and said corresponding predetermined range wherein said storage means stores two sets of ranges for at least one of said parameters.