A simple circuit based on a Wheatstone bridge is described which enables temperature readings to be obtained directly in degrees Celsius with a platinum resistance thermometer, without the use of correction or calibration tables. Irrespective of the inaccuracy of the thermometer itself, reading accuracy is to better than ±0·1 degC for a temperature range from 0 to +500°C. Variation in the sensitivity of the bridge can be less than 15% in the same temperature range.