Pulse-based impedance measurement instrument

A pulse-based impedance measurement instrument, comprising:

• (a) an instrument connector for coupling to a device under test;
• (b) a pulse generator coupled to said instrument connector for repetitively generating stimulus pulses across said device under test;
• (c) a digital sampling circuit coupled to said instrument connector for repetitively sampling a response signal from said device under test at selected time delays from said stimulus pulse and providing digital measurement values;
• (d) an acquisition memory coupled to said digital sampling circuit for receiving said digital measurement values, said acquisition memory storing said digital measurement values in memory locations corresponding to said selected time delays to build a time record of said response signal;
• (e) a microprocessor coupled to said acquisition memory to receive said time record, wherein said microprocessor:
• performs a fast Fourier transform on said time record to obtain a frequency domain representation, and
• calculates a set of complex impedance values of said device under test using said frequency domain representation and a set of calibration constants derived from measurements of a set of calibration resistors;
• and
• (f) a display coupled to said microprocessor to visually display said set of complex impedance values.

A pulse-based method of measuring complex impedance, comprising:

• (a) measuring a plurality of calibration resistors to obtain calibration time records;
• (b) calculating a fast Fourier transform of each of said calibration time records to produce a plurality of calibration frequency domain representations;
• (c) calculating a set of calibration constants from said calibration frequency domain representations;
• (d) measuring a device under test to produce a time record;
• (e) calculating a fast Fourier transform of said time record to produce a frequency domain representation;
• (f) calculating a set of complex impedance values from said frequency domain representation and said set of calibration constants;
• and
• (g) visually displaying said set of complex impedance values.