Capacitance probe for fluid flow and volume measurements

DETAILED DESCRIPTION The present invention provides method and apparatus for making measurements on a fluid flow stream which may include multi-phase flow that may have a gas as one phase.
In a specific embodiment of the present invention, measurement is made of a volume of urine entrained within an air stream.
In this manner, the present invention is especially adapted for measurement of urinary output in a micro-gravity environment.
More generally, an electromagnetic flow monitor is provided for monitoring flow of a material within a flow stream.
The flow monitor includes a first probe having first and second elongate electrodes substantially parallel with respect to each other.
The spacing between the electrodes is functionally related to the fluid to be monitored.
Generally, the spacing between the electrodes should be small enough that both electrodes will engage the fluid.
More specifically, the spacing will typically be related to the size of a droplet of the fluid which size may depend on the fluid, the flow speed, the temperature, the flow stream within which it is entrained, and other related factors.
A signal generator is operative to produce a reference signal for the probe.
A cable is utilized for applying the reference signal to the probe and conducting a reflection signal to detection circuitry that is responsive to the permittivity of the flow stream between the first and second elongate electrodes by producing an analog permittivity signal.
A second probe is also preferably provided to measure conductivity.
The detection circuitry is responsive to the conductivity of the material for producing an analog conductivity signal.
Analog to digital conversion circuitry converts the analog permittivity signal and the analog conductivity signal, respectively, to a digital permittivity signal and a digital conductivity signal.
Calculating circuitry combines the digital permittivity signal and the digital conductivity signal to provide an output related to flow of the material within the flow stream