Time-base generator with self-compensating control loop
AssigneeSiemens Milltronics Process Instruments, Inc.
InventorQuinton Lyon
Life of this patent
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Abstract
A time-base generator with a self-compensating control loop. The time-base generator is suitable for use in level measurement and time-of-flight ranging systems. The time-base generator includes a pulse generator stage, a delay stage, a control loop and a references voltage module. The pulse generator generates a transmit pulse train and a receive or sampling pulse train with a delayed timing relationship. The control loop functions with the delay stage to maintain the desired delay between the first pulse train and the second pulse train. According to another aspect, the time-base generator includes a calibration module. The calibration module generates calibration pulses which are used by the controller in the level measurement system to calibrate operation.
Claims12
A time-base generator suitable for use in an echo ranging system, said time-base generator comprising:
- (a) a first pulse generator having an input for receiving an input signal and generating an output pulse train from said input signal;
- (b) a second pulse generator having an input for receiving a delayed signal and generating a delayed output pulse train, said delayed output pulse train having pulses with leading edges delayed from pulses in said output pulse train;
- (c) a delay stage coupled to the input of said second pulse generator, said delay stage having an input for receiving said input signal and an output coupled to the input of said second pulse generator for outputting said delayed signal, and said delay stage including a control input for varying the delay in said delayed signal in response to a delay control signal;
- (d) a control loop having an input port and output port, said output port being coupled to the outputs for said first and said second pulse generators, and said control loop having an output port coupled to the control input of said delay stage for outputting said delay control signal;
- and
- (e) a references voltage module having one or more components for setting reference voltage outputs, and said references voltage outputs providing a temperature independent effect for components in said first and said second pulse generators and in said delay stage and said control loop.
A method for calibrating a level measurement system, the level measurement system including a transmit module, a receive module, a transducer, and a controller, the transmit module is responsive to the controller to generate transmit pulses from the transducer, and the receive module is responsive to echo signals received from the transducer for processing by the controller to generate an echo profile, said method comprising the steps of:
- (a) providing a first reflective surface at a first distance from the transducer;
- (b) providing a second reflective surface at a second distance from the transducer, and said second reflective surface being movable to provide an unobstructed path between said first reflective surface and the transducer;
- (c) generating one or more pulses directed at said second reflective surface and taking time of flight measurements for pulses reflected by said second reflective surface;
- (d) moving said second reflective surface to provide the unobstructed path to said first reflective surface;
- (e) generating one or more pulses directed at said first reflective surface and taking time of flight measurements for pulses reflected by said first reflective surface;
- (f) providing first and second calibration pulses;
- (g) using a sampling signal to determine an echo time for each of said calibration pulses;
- (h) determining a corresponding distance for each of said calibration pulses, said distances being based on said first and second distances, said time of flight measurements, and said echo times;
- (i) calibrating said sampling signal using the distances for each of said calibration pulses.
Dependencies are inferred from the claim text.