A two phase AC-bridge as a basis for in situ measurements of different physical parameters

It is shown that it is possible to design an ac-voltage bridge consisting only of real resistances without reactances to measure phaseshifts. Such a bridge is realised through two supplies for the two branches of the ac-voltage bridge, in such a way that if the supply for one branch is given by the vector voltage U, the supply for the other branch must then be given by j.U that means by an ac-voltage with a phaseshift of 90°. This bridge has been studied with the result that it may be realised for measuring temperature with a platinum wire to an accuracy of 0.002°C over a whole range of 40°C. A circuit for the realisation of such a bridge is described.