Research and Testing

Equipment, Programmes, Techniques and Projects. The high precision resistance bridge, Type 5577, recently introduced by H. Tinsley and Co. Ltd., Werndee Hall, South Norwood, London, S.E.25, is said to eliminate switching errors usually associated with the Wheatstone‐bridge type of measuring instrument, together with a reduction of possible errors, or damage, due to excessive current in one or more coils. These advantages are attributable to circuitry design. The variable arm incorporated in the bridge is constructed of conductance elements, built‐up in binary increments, and covers a million steps. Six coils only are used on each of six decades; a total number of thirty‐six instead of the sixty coils normal to a conventional Wheatstone‐bridge circuit. Ratios are changed by means of a rotary switch.