Temperature compensation in indicating and recording instruments

One cause of errors in indicating and recording instruments is their use at a temperature other than that at which they were calibrated. Most of the physical properties of materials on which the performance of an instrument depends, vary to a greater or less degree with temperature. It is therefore necessary when designing an instrument to reduce to a minimum any errors caused by changes in temperature, and if possible to make them negligibly small. This is done either by adopting a design such that the temperature errors themselves are very small, or by introducing other changes with temperature which will compensate them. An account is given in the paper of the more common methods employed, each method being briefly discussed to indicate the best arrangement for each type of instrument. The instruments considered are ammeters, voltmeters, millivoltmeters, wattmeters, and rectifier-operated and thermocouple instruments.