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Method and device for monitoring an insulating or conducting test fluid for acidity, basicity, contaminants and/or specific chemicals by monitoring the rate of modification, for example corrosion, dissolution or erosion of at least one plate of a capacitive sensor immersed in the fluid. The sensor's

Method and device for monitoring an insulating or conducting test fluid for acidity, basicity, contaminants and/or specific chemicals by monitoring the rate of modification, for example corrosion, dissolution or erosion of at least one plate of a capacitive sensor immersed in the fluid. The sensor's dielectric element is inorganic or piezoelectrically active ceramic. Capacitor plates can be different materials, foil or coated/deposited metals modified by the test fluid. Capacitance is measured over time, its change due to modification of sensor plate area is recorded and used to determine quantity of acid, alkali, contaminants and/or chemicals in the test fluid. Piezoceramic dielectric allows the detector to be vibrated. The sensor can be attached to an ultrasonic transducer. Presence of specific chemicals requires a chemically non-reactive and a chemically reactive electrode re the chemical of interest. If the test fluid is conductive, the changed capacitance is measured in an insulating fluid.

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Method and device for monitoring an insulating or conducting test fluid for acidity, basicity, contaminants and/or specific chemicals by monitoring the rate of modification, for example corrosion, dissolution or erosion of at least one plate of a capacitive sensor immersed in the fluid. The sensor's

Method and device for monitoring an insulating or conducting test fluid for acidity, basicity, contaminants and/or specific chemicals by monitoring the rate of modification, for example corrosion, dissolution or erosion of at least one plate of a capacitive sensor immersed in the fluid. The sensor's dielectric element is inorganic or piezoelectrically active ceramic. Capacitor plates can be different materials, foil or coated/deposited metals modified by the test fluid. Capacitance is measured over time, its change due to modification of sensor plate area is recorded and used to determine quantity of acid, alkali, contaminants and/or chemicals in the test fluid. Piezoceramic dielectric allows the detector to be vibrated. The sensor can be attached to an ultrasonic transducer. Presence of specific chemicals requires a chemically non-reactive and a chemically reactive electrode re the chemical of interest. If the test fluid is conductive, the changed capacitance is measured in an insulating fluid. itively measuring electrical rotational position of the spindle motor until a transition to the next commutation state is detected; and (a4) repeating steps (a2) and (a3) until the first velocity is reached. 4. The method of claim 3, wherein the electrical rotational position of the spindle motor is determined during step (a3) by steps of: (a3i) sequentially applying sense pulses to the spindle motor; and (a3ii) measuring a corresponding rise time for a resulting voltage induced by application of each said sense pulse, said rise time determined in relation to impedance of the spindle motor determined in turn by the electrical rotational position of the spindle motor. 5. The method of claim 1, wherein step (b) comprises steps of: (b1) measuring the most recent commutation period; (b2) calculating a drive pulse duration in relation to the most recent commutation period and a scale factor so that the drive pulse duration is less than the most recent commutation period; (b3) applying a drive pulse with the calculated drive pulse duration of step (b2) to the spindle motor; (b4) repetitively measuring electrical rotational position of the spindle motor until a transition to the next commutation state is detected; and (b5) repeating steps (b1) through (b4) until the intermediate velocity is reached. 6. The method of claim 5, wherein the electrical rotational position of the spindle motor is determined during step (b4) by steps of: (b4i) sequentially applying sense pulses to the spindle motor; and (b4ii) measuring a corresponding rise time for a resulting voltage induced by application of each said sense pulse, said rise time determined in relation to impedance of the spindle motor determined in turn by the electrical rotational position of the spindle motor. 7. The method of claim 5, wherein the scale factor used to calculate the drive pulse duration during step (b2) is a constant. 8. The method of claim 5, wherein the scale factor used to calculate the drive pulse duration during step (b2) varies in relation to the rotational velocity of the spindle motor as the spindle motor accelerates from the first velocity to the intermediate velocity. 9. A disc drive, comprising: a brushless direct current (dc) spindle motor configured to rotate at least one recording disc; a read/write head configured to write data to the disc and read data from the disc as the spindle motor is rotated at a final operational velocity; back electromagnetic force (bemf) detection circuitry coupled to the spindle motor and which detects bemf from rotation of the spindle motor above a medium velocity, the medium velocity less than the final operational velocity; commutation circuitry coupled to the bemf detection circuitry and spindle motor which electrically commutates the spindle motor in relation to the detected bemf over a range of commutation states of the spindle motor; and a control circuit which accelerates the spindle motor by applying variable duration drive pulses to the spindle motor and measuring electrical rotational position to detect successive spindle motor commutation state transitions without relying upon bemf from the spindle motor, wherein the variable duration of each successive drive pulse is established in relation to a most recent commutation period comprising the elapsed time between the two most recently detected state transitions, and wherein each of the variable duration drive pulses is applied during a different commutation period. 10. The disc drive of claim 9, wherein the control circuit subsequently directs the bemf detection circuitry and the commutation circuitry to accelerate the spindle motor from the medium velocity to the final operational velocity in relation to the detected bemf from the spindle motor. 11. The disc drive of claim 9, further comprising spindle driver circuitry coupled to the spindle motor and the commutation circuitry and which applies drive pulses to each of a plurality of