An opaque sensing device having a light-dependent resistor and a light source spaced apart so that material to be analyzed can be passed between them. The light-dependent resistor is connected to an impedance, such as a series resistor, across a voltage source to cause a fraction of the voltage to be present across the light-dependent resistor. A light source, such as a neon bulb, provides the only illumination to the resistor, and the impedance of the latter is therefore a measure of the opacity of the light path. When this sensing system is immersed in a septic tank, the buildup of sludge in the tank eventually reaches a level at which the light is interrupted, and the resistance of the light-dependent resistor changes, resulting in a change in voltage across it. This voltage is measured by an indicator outside of the septic system to determine when the sludge level has reached the immersed unit. The indicator may consist of a second neon bulb electrically connected across the light-dependent resistor. A normally closed switch may also be connected in series with the light source to interrupt current to the latter in order to create the effect of opaque matter to determine whether the indicator light will properly show a condition of opacity.
A liquid level sensing device, particularly useful for apparatus designed to humidify oxygen gas being administered to patients undergoing respiratory therapy is disclosed. The liquid level sensing device detects the liquid level in a canister having an optical probe therein. A bracket, rotatable on a frame of the device, carries a light source and a light sensing member for determining liquid level in the canister in conjunction with the probe. The hinged bracket engaging relation, and it also rotates out of probe-engaging relation and registry with the light probe. When the bracket is out of registry with the light probe, the canister may be removed and replaced. The bracket may be releasably retained out of probe-engaging relation by means of a snap fit structure.
Apparatus for providing an electrical signal when developer material for a copy machine recedes to predetermined level in a container for the material. The apparatus is positioned within the container and includes a light generating means directing light to a light to electric transducer. A cleaning member carried by a rotating arm is included which with rotation of the arm displaces any developer material that is present between the light generating means and the transducer means.
A sludge blanket-clarified liquid interface detector apparatus for a wastewater treatment process including a floating decanter assembly preferably includes a sludge detector light source and light sensor pair positioned in spaced apart relation on a sludge layer detector frame which is suspended in depending relation below the floating decanter assembly. The light sensor is interfaced to a process controller to which is also interfaced a decanter valve which flow controls the decant cycle of the process. As the decant cycle proceeds, the decanter assembly descends along with the falling level of liquid in the process reactor until the detector descends past the interface and into the sludge layer. The decrease in light transmission between the light source and sensor is signaled to the controller which causes the decanter valve to close to end the decant cycle to prevent the discharge of polluting sludge from the reactor.
