Fluid density and viscosity measurement tool with noise cancellation

A system comprising:

• a tool configured for insertion into a wellbore;
• a sensor housing comprising an upper sensor housing and a lower sensor housing, wherein the sensor housing is connected to the tool, and wherein a channel is disposed between the upper sensor housing and the lower sensor housing;
• a cantilever beam connected to a stem extending from the upper sensor housing or the lower sensor housing and disposed within the channel;
• an actuator located in an equipment cavity in the lower sensor housing, the actuator connected to the cantilever beam through the lower sensor housing and configured to cause the cantilever beam to vibrate;
• a sensor connected to the cantilever beam and configured to generate a first signal representing a cantilever beam vibration of the cantilever beam;
• a membrane formed from the lower sensor housing and disposed at the stem between the actuator and the cantilever beam such that the membrane and the lower sensor housing form a cavity between the actuator and the membrane, the cavity being disposed between the actuator and the cantilever beam, wherein the cavity has a toroidal shape in the lower sensor housing at the stem to reduce a mass of the lower sensor housing at the stem and decrease a vibration dampening effect of the mass of the lower sensor housing, wherein the membrane transfers vibrations between the actuator and the cantilever beam through the stem;
• an accelerometer connected to the sensor, the accelerometer configured to generate a second signal representing an external vibration of the lower sensor housing, wherein the external vibration changes the cantilever beam vibration;
• and
• a signal processor configured to receive, as input, the first signal and the second signal and to generate, as output, a filtered signal that reduces an effect of the external vibration on the cantilever beam vibration.

A method comprising:

• vibrating, using an actuator, a cantilever beam in a fluid disposed in a channel of a sensor housing, wherein the sensor housing comprises an upper sensor housing and a lower sensor housing and the channel is disposed between the upper sensor housing and the lower sensor housing and is subject to an external vibration, wherein the cantilever beam is vibrated using an actuator;
• generating a first vibration signal of the cantilever beam as the cantilever beam vibrates in the fluid, wherein the first vibration signal is generated using a sensor connected to the sensor housing, wherein a membrane is formed from the lower sensor housing and disposed between the actuator and the membrane such that a cavity is formed between the actuator and the membrane, the cavity being disposed between the actuator and the cantilever beam, wherein the cavity has a toroidal shape in the lower sensor housing at the membrane to reduce a mass of the lower sensor housing at the cantilever beam and decrease a vibration dampening effect of the mass of the lower sensor housing, wherein the membrane transfers vibrations between the actuator and the cantilever beam;
• generating a second vibration signal of an accelerometer that is connected to one of the sensor and the sensor housing;
• and
• filtering the second vibration signal from the first vibration signal to generate a filtered output.