TF1313A Universal Bridge

This excellent 0.1 % grade bridge measures DC resistance and AC impedances (capacitance, inductance and corresponding loss angles). A Wheatstone bridge arrangement is used for the resistance measurements. This bridge is modified by adding capacitive (and associated loss angle) components for impedance measurement. Various configurations of this theme give the bridge the ability to measure capacitance and inductance in series or parallel modes.

The neat plastic booklet fitted to the top of the bridge gives detailed instructions on its use, including the procedure to apply corrections for residual impedances.

The instrument features a very sensitive built-in detector and a 1 kHz / 10 kHz oscillator. An external AC stimulus, and DC bias, can also be used.

To the best of my recollection, this was the last MI product that used thermionic valves. It even has a proper Mullard EF86!

This one is in good working order and is still well within its 0.1 % specification.