Preamplifier and method for measuring resistance of a resistive transducer

A preamplifier for a resistive transducer, configured to generate an amplified output indicative of potential difference across the transducer (while the transducer is biased and in the presence of a magnetic field) and to generate a resistance signal indicative of the transducer's resistance, and a method for measuring the resistance of a resistive transducer during operation of the transducer in the presence of a changing magnetic field. The preamplifier preferably includes circuitry for generating a current signal indicative of the instantaneous current through the transducer and analog divider circuitry for generating the resistance signal from a signal indicative of the potential difference across the transducer and the current signal. When the resistance signal is an analog signal, the preamplifier can include circuitry for processing the analog resistance signal to generate a word of binary data indicative of a value proportional to the transducer resistance. Alternatively, when the resistance signal is an analog signal the preamplifier can include a digital-to-analog (D-to-A) converter, and a comparator which receives an analog resistance signal and the output of the D-to-A converter. In operation of the latter class of embodiments, the output of the D-to-A converter is swept until the comparator is tripped, at which time the setting of the D-to-A converter is proportional to the transducer resistance.