Drop detection method and apparatus

A method for detecting drops passing through a substantially hollow drop chamber having an inlet end and an opposed outlet end and also having an outer wall, comprising the steps of:

• passing light from a light source through the drop chamber;
• detecting light after it has passed through the drop chamber and producing an electrical output signal related thereto;
• blocking the DC component of the output signal while transmitting frequency components at and above a predetermined threshold level to produce a filtered output signal;
• and
• determining variations in the filtered output signal to determine that a drop has passed through the drop chamber.

A method for detecting drops passing through a substantially hollow drop chamber having an inlet end and an opposed outlet end and also having an outer wall, comprising the steps of:

• passing light from a light source positioned at a first focal point of an ellipse through the drop chamber;
• reflecting the light passed through the drop chamber off of an elliptical reflecting surface defined by the portion of the surface of an ellipse having a first focal point and a second focal point, said first focal point being relatively farther from said reflecting surface and said second focal point;
• and,
• detecting the light reflected off of said elliptical reflecting surface and producing an electrical output signal related thereto;
• and,
• determining variations in the output signal to determine that a drop has passed through the drop chamber.

A method for detecting drops passing through a substantially hollow drop chamber having an inlet end and an opposed outlet end and also having an outer wall comprising the steps of:

• passing light from a light source positioned at a first focal point of an ellipse through the drop chamber and into a light pipe made of a material transparent to light, said light pipe having an outer surface defined by a portion of the surface of said ellipse having said first focal point and a second focal point, said outer surface having a reflective coating so that light from within said light pipe striking said outer surface will be reflected back into said light pipe;
• reflecting the light passed through the drop chamber off said reflective coating on said outer surface;
• detecting the light reflected off of said reflective coating on said outer surface and producing an electrical signal related thereto;
• and,
• determining variations in the output signal to determine that a drop has passed through the drop chamber.

A drop flow detector comprising:

• a substantially hollow drop chamber having an inlet end and an opposed outlet end, said drop chamber having an outer wall;
• means for detecting a drop passing from said inlet end to said outlet end, the drop passing either in a vertical direction or at an angle varied from the vertical direction including the drop moving along said outer wall of said drop chamber, said means for detecting a drop including:
• a reflector having an elliptical reflecting surface, said elliptical reflecting surface defined by a portion of the surface of an ellipse having a first focal point and a second focal point, said first focal point being relatively farther from said reflecting surface than said second focal point;
• a light source positioned at said first focal point, said light source directed through said drop chamber and toward said reflecting surface;
• and,
• means for detecting light emitted from said light source.

A drop flow detector comprising:

• a substantially hollow drop chamber having an inlet end and an opposed outlet end, said drop chamber having an outer wall;
• means for detecting a drop passing from said inlet end to said outlet end, the drop passing either in a vertical direction or at an angle varied from the vertical direction including the drop moving along said outer wall of said drop chamber, said means for detecting a drop including:
• a light pipe made of a material transparent to light, said light pipe having an outer surface defined by a portion of the surface of an ellipse having a first focal point and a second focal point, said outer surface having a reflective coating so that light from within said light pipe striking said outer surface will be reflected back into said light pipe, said first focal point being relatively farther from said reflecting outer surface than said second focal point, said light pipe placed near said drop chamber;
• a light source positioned at said first focal point, said light source directed through said drop chamber and towards said reflecting outer surface;
• and
• means for detecting light emitted from said light source.

A drop flow detector comprising:

• a substantially hollow drop chamber having an inlet end and an opposed outlet end, said drop chamber having an outer wall;
• means for detecting a drop passing from said inlet end to said outlet end, the drop passing either in a vertical direction or at an angle varied from the vertical direction including the drop moving along said outer wall of said drop chamber, said means for detecting a drop including:
• circuit means responsive to the output signal of said light detector for determining the existence of drop flow;
• blocking means for blocking the DC component of the output signal of said light detector from transmission to said circuit means, said blocking means transmitting frequency components at and above a predetermined threshold frequency to produce a filtered output signal;
• and
• low pass filtering means for blocking the frequency components in said output signal from said light detector having a frequency above a predetermined cutoff frequency, said filtering means having a variable cutoff frequency, said filtering means further having a control input for receiving a signal which determines said predetermined cutoff frequency.