A method, consisting of acquiring signals, indicative of temperatures at respective locations in a biological tissue, from a plurality of thermal sensors mounted on a probe in contact with the tissue, interpolating between the temperatures so as to produce a temperature distribution map, and displaying the temperature distribution map on a screen. The method also includes determining that at least one of the thermal sensors is a malfunctioning thermal sensor, and that remaining thermal sensors of the plurality are correctly operating. The at least one malfunctioning thermal sensor is assigned a first arbitrary temperature and the correctly operating thermal sensors are assigned second arbitrary temperatures. The method further includes interpolating between the first and second arbitrary temperatures so as to produce an error distribution map indicative of a suspect portion of the temperature distribution map, and superimposing graphically the error distribution map on the displayed temperature distribution map.
