Digital flowmeter
View Patent ↗A control and measurement system for a coriolis flowmeter having a flowtube, a driver adapted to vibrate the flowtube, and a pair of sensors adapted to generate signals indicative of movement of the flowtube when it is being vibrated by the driver, wherein the sensors are positioned relative to one another so the signals from the sensors are indicative of a mass flow rate of fluid through the flowtube. A digital drive signal generator is adapted to generate a variable digital drive signal for controlling operation of the driver. The digital drive signal generator can be adapted to cause the driver to resist motion of the flowtube during a first time period and amplify motion of the flowtube during a second time period. The digital drive signal generator can also be adapted to initiate motion of the flowtube by sending one or more square wave signals to the driver.
1. A control and measurement system for a Coriolis flowmeter of the type comprising a flow tube, a driver configured to oscillate the flow tube, and a pair of sensors configured to generate signals indicative of movement of the flowtube when it is being oscillated by the driver, the sensors being positioned relative to one another so the signals from the sensors are indicative of a mass flow rate of fluid through the flowtube, the control and measurement system comprising:
a signal processor configured to determine the mass flow rate of the fluid using the sensor signals and output a signal indicative of the determined mass flow rate; and
a digital drive signal generator configured to generate a variable digital drive signal for controlling operation of the driver, wherein the drive signal generator is configured to adjust a phase of the digital drive signal to compensate for a time delay associated with the components connected between the sensors and the driver.
2. A control and measurement system as set forth in claim 1 wherein the digital drive signal generator is configured to synthesize the drive signal.
3. A control and measurement system as set forth in claim 1 wherein the signal processor is configured to determine the mass flow rate of the fluid using a phase difference between the sensor signals.
4. A control and measurement system as set forth in claim 1 further comprising a digital low pass filter configured to receive the sensor signals and suppress frequency content in the sensor signals above a cutoff frequency, the signal processor being configured to determine the mass flow rate of the fluid using the filtered sensor signals from the digital low pass filter and the digital drive signal generator being configured to adjust a phase of the digital drive signal to compensate for a time delay associated with the low pass filter and other components connected between the sensors and the driver.