Abstract:
420D-165 Canada METHOD AND APPARATUS FOR MONITORING LIGHT SIGNALS FROM LIQUID MEDIUM In processes for detection and measuring a substance or condition in a fluid medium by the effect of the substance or condition on a light emitting substance, such as luminous microorganisms, disposed in the medium, a method and apparatus is provided for determining the effect of the medium on the light signal due to the medium absorbancy or other factor which is independent of the effect of the substance or condition on the light emitting substance. This is accomplished by deriving from the transmittance of the fluid medium using an external light source the expected transmittance of the fluid medium containing the light emitting substance according to the expression where A is the absorbancy of the fluid, c is the concentration of the absorbing substance and D is the mean absorbtion path length of the photons emitted. The expected transmittancy is applied to the observed transmittancy of the test sample to obtain the transmittancy of the test sample independently of the optical effects of the medium. A cell design is disclosed for determining the absorbancy of the fluid medium using a single instrument.
Abstract:
In a sensor for measuring the quantity of a substance in a compositionof matter of the type including a membrane which is permeable to the substance and substantially impermeable to liquid and ions, the permeability of the membrane being a function of the pressure thereon, the sensor providing an electrical output signal which is a function of the quantity of the substance in the composition of matter, there is disclosed an improvement consisting of a method and means for accurately compensating the output of the sensor for the effect of pressure upon membrane permeability by multiplying the output signal by the function ekp thus cancelling the pressure effect which is given by the function Poe-kp where Po=membrane permeability at zero pressure, p=absolute pressure, and k=a membrane constant. According to a preferred embodiment of the invention, such multiplication is achieved through the use of a pressure-driven, variable resistance in the feed-back loop of an operational amplifier.
Abstract:
420D 145 Canada A sample holder and shutter assembly for photometers is disclosed in which a stationary sample chamber body is mounted in close proximity to a photosensitive device. A light path is provided from the sample chamber to the photosensitive device and shutter means is provided for selectively interrupting and opening the light path between the photosensitive device and the sample chamber without moving the sample chamber. Heat exchange means including a heat pump and a heat reservoir are provided for maintaining a desired temperature in the sample chamber. The sample chamber body is thermally connected to said heat pump and is preferably thermally isolated from the means mounting it. In one embodiment, the heat pump and heat reservoir are flexibly connected.
Abstract:
Apparatus for determining the partial pressure of a paramagnetic gas in a gas mixture wherein a pivotally mounted test body is supported in an inhomogeneous magnetic field, the test body being deflected from a null position when the paramagnetic gas is present, the improvement wherein an AC bridge circuit is utilized, in response to deflection of the test body from the null position, to generate an AC signal indicative of the partial pressure of the paramagnetic gas. The bridge circuit comprises a pair of electrostatic vanes which, in conjunction with the test body, form capacitive elements of the bridge circuit. The AC signal is either measured to determine the test body position, or demodulated to provide a DC signal. The DC signal may be fed back to the bridge circuit to return the test body to the null position for improved linearity and stability. Apparatus is further provided to vary the fraction of the DC signal fed back to the bridge circuit with changes in temperature of the test body to compensate the apparatus for temperature variations.