Apparatus and method for detecting liquid level in a clear or partially clear container

1. A filter trap apparatus, comprising:

a trap bowl configured to accumulate liquid droplets from a filter, as a liquid content, comprising a transparent circumferential prism, having a face that forms a circumferential interior surface of the trap bowl, the face having a first angle of total reflection when a gas is against the circumferential interior surface, and a second angle of total reflection when the liquid content is against the circumferential interior surface;

a light source, configured to emit a light beam incident on the face at an angle of incidence; and

a light receiver, wherein the angle of incidence results in reflection of the light beam, striking the light receiver, when the face has the first angle of total reflection, and results in refraction of the light beam, missing the light receiver, when the face has the second angle of total reflection,

wherein the face is an upper face, wherein the circumferential interior surface of the trap bowl is an upper circumferential interior surface, wherein the transparent circumferential prism further comprises a lower face, wherein the lower face forms a lower circumferential interior surface of the trap bowl, and wherein the upper face and the lower face form an included angle that opens outwardly, circumferentially around the trap bowl,

wherein the upper face and the lower face intersect at a vertex, the vertex being circumferential around the trap bowl, and wherein the included angle is arranged symmetrically about a reference bisector line the extends outward from the vertex,

wherein the light source is configured to emit the light beam as a collimated light beam, and to emit the collimated light beam in a direction approximately parallel to the reference bisector line, and

wherein, irrespective of rotational orientation of the trap bowl, the angle of incidence results in reflection of the light beam, striking the light receiver, when the face has the first angle of total reflection, and results in refraction of the light beam, missing the light receiver, when the face has the second angle of total reflection.

2. The filter trap apparatus of claim 1 , further comprising the filter, wherein the filter includes an ingress passage, an egress passage, and an intermediate passage, wherein the filter is configured to receive at the ingress passage samples of a therapeutic gas, remove the liquid droplets from the therapeutic gas to form a filtered therapeutic gas, deliver the liquid droplets through the intermediate passage, and output the filtered therapeutic gas from the gas egress passage.

3. The filter trap apparatus of claim 1 , wherein the reference bisector line extends in a reference cone that is circumferential about the trap bowl and contains the vertex.

4. The filter trap apparatus of claim 1 , wherein the included angle is approximately 90 degrees.

5. The filter trap apparatus of claim 4 , wherein the angle of incidence is approximately 45 degrees.

6. The reference trap apparatus of claim 1 , wherein the transparent circumferential prism further includes a light beam receiving face, wherein the collimated light beam is incident to the light beam receiving face at a point of incidence.

7. The filter trap apparatus of claim 6 , wherein the included angle is approximately 90 degrees, the angle of incidence is approximately 45 degrees, and wherein the light beam receiving face is a bevel that extends circumferentially around an outer surface of the trap bowl.

8. The filter trap apparatus of claim 1 , further comprising the filter, wherein the filter included an ingress passage, an egress passage, and an intermediate passage, wherein the filter is configured to receive at the ingress passage samples of a therapeutic gas, remove the liquid droplets from the therapeutic gas to form a filtered therapeutic gas, deliver the liquid droplets through the intermediate passage, and output the filtered therapeutic gas from the gas egress passage.