Abstract: A contamination meter (1) for measuring salt concentration on a surface by measuring the electrical resistance of a test medium which has been applied to the surface is disclosed. The meter (1) has at least two electrodes (9) arranged to be brought into contact with the test medium. A measuring device is arranged to measure the electrical resistance of the test medium between one or more pairs of electrodes (9), thereby to measure the electrical resistance of the test medium between the or each pair of electrodes (9) when the electrodes (9) are brought into contact with the test medium. The electrodes (9) are arranged such that, in use, the resistance of the test medium is measurable between pairs of electrodes (9) at different positions on the medium without any relative movement between the medium and the contamination meter (1). The electrodes (9) may be arranged in a grid, and an electrical resistance measurement may be made between any pair of electrodes (9).