Abstract: A method for measuring the dew point according to patent application P 36 33 015 is expanded so that an automatic zero point correction can be carried out. For this purpose, the heating power on the heating device is raised to a point, at which the dew evaporates and the sensor-specific property, for example the capacity, is measured and supplied to the evaluating unit as a calibration signal.

Abstract: A dewpoint meter has a sensor comprising a mirror (1) situated in a chamber (2) through which gas, the dewpoint of which is to be measured is passed through an inlet port (3) and an outlet port (4). The mirror (1) is cooled by a Peltier effect heat pump (11) and the formation of condensation on the mirror as it is cooled is detected by a detector comprising a light emitting diode (7) and a photodiode (8). The temperature at which condensation occurs, which is the dewpoint of the gas, is measured by a thermometer. Instead of transferring the heat from the heat pump (11) directly to a heat sink (13) as is usual, a heat pipe (12) is interposed between the heat pump (11) and the heat sink (13). This avoids the necessity for having the heat sink closely adjacent the mirror and thus avoids errors caused by heat from the heat sink affecting the temperature of the mirror.

Abstract: A radiation source directs light at a mirror which reflects to a first photosensor. As a dew point is reached, scattered light is reflected to a second photosensor to indicate dew point. Rather than periodically interrupting operation to test reflectivity of the mirror or to perform a heating cycle, operation is monitored continuously. The common mode output of both the first and second photosensors is monitored. When below a threshold level, the output indicates the need for cleaning the mirror. It may also be used in a closed loop to increase light source intensity as mirror reflectivity decreases.

Abstract: To measure the heat transfer coefficient of a sample, an element with temperature sensitive optical properties is placed in contact or implanted in the sample. The element is heated or cooled. The temperature difference between the element and the unheated sample and the rate of heating or cooling indicate the heat transfer coefficient of the sample. In one embodiment, the element is heated or cooled at a constant rate. The heat transfer coefficient of the sample is then inversely related to the difference in temperature between the element and the unheated sample. Alternatively, the element may be heated or cooled at such a rate that the temperature difference between the element and the unheated sample remains substantially constant. The heat transfer coefficient of the sample then varies directly with the rate of heating or cooling. The heat transfer coefficient of a sample is a measure of its composition and other physical properties.

Abstract: Energy transmitted to a load in a fluid medium is measured utilizing a probe having an elongate heat transmitter that includes a sensing tip at one end, a heat exchanger at its opposite end, a thermal impedance forming at least a segment of the heat transmitter, and temperature sensors spaced apart along the impedance. The temperature of the sensing tip is maintained different from that of the sensed fluid. A read-out is responsive to the temperature sensors and it is calibrated in terms of the energy content of the fluid flowing in the sensed passage. Corrections for various factors of error are incorporated in the read-out. A relative simple yet reasonably accurate measure is made of the energy in steam, where the heat exchanger of the probe is a passive heat dissipator.

Abstract: A method and apparatus for determining the presence or absence of a pour point depressant additive in hydrocarbon liquids includes cooling a sample of the liquid at a predetermined cooling rate from a temperature substantially above the cloud point temperature of the sample liquid to a temperature substantially below the cloud point temperature of the sample liquid. The points on the cooling rate curve for the sample at which a deflection of the curve begins and ends is determined and the time interval between the beginning and ending points of the cooling rate curve is computed. This computed time interval between the beginning and ending points is compared to a reference time interval such that if the reference time interval is less than or greater than the computed time interval between the beginning and ending points on the cooling curve, the presence or absence, respectively, of a pour point depressant additive in the sample is determined.

Abstract: A method and apparatus for determining the saturation temperature of a solution containing a dissolved substance, the crystals of which are optically anisotropic. The solution is placed in an optical measurement vessel under conditions wherein crystals of said substance are present, and the temperature of said crystal containing solution is gradually increased to at least the temperature at which all of the crystals dissolve. The temperature of the solution is continuously measured. Simultaneously with the temperature increase, a beam of linearly polarized light is directed into the optical measurement vessel in a manner such that it is transmitted through said solution; the transmitted beam of light, after having passed through the solution, is directed through a light polarizing analyzer having a direction of polarization normal to that of said beam of light; and at least a portion of any light transmitted through said analyzer is directed to a light measuring photodetector.

Abstract: A controlled power conversion system for providing power to a thermoelectric heat pump for controlling the temperature of a device, such as a chilled mirror used in a chilled mirror humidity sensor. The system uses means, responsive to a DC input power source and to a control signal representing changes in the temperature of the device, for providing periodic pulses of the DC input power having a duty cycle which is controllable in accordance with the control signal. The input power is time-averaged and an energy storage means, responsive to the periodic pulses of DC input power, is utilized to provide a controllable time averaged DC power output to the heat pump.

Abstract: A computer cooling system has a mixing valve which supplies coolant to the computer and receives hot return coolant from the computer and also chilled return coolant from a chiller intermediate the computer and the mixing valve. The mixing valve mixes the hot return coolant with the chilled return coolant to adjust the cooling system temperature. Control circuitry senses, or estimates, the dew point temperature of the computer room environment, compares it with the cooling system temperature, and adjusts the mixing valve to maintain the cooling system temperature a few degrees above the dew point temperature. A condensation sensor comprised of a light emitting diode (LED), reflective tape applied about a cooling system supply conduit, and a phototransistor is disclosed. Light from the LED is fully reflected by the reflective tape to the phototransistor in dry conditions, but only partially reflected when condensation forms on the tape.

Abstract: Liquid hydrocarbon samples from a mainstream are diverted through a sample cell in cooling chamber. An optical cloud point detector signals a microprocessor-based control system which controls the charging and cooling of the cell. Cloud point reference level is continuously updated. After each measurement cycle, the control system readjusts the cooling power so that the time interval between the end of the flush cycle and cloud point detection is brought within a predetermined range. The control system switches between several distinct modes of operation automatically.

Abstract: An integrated circuit device is disclosed for sensing dew point which uses integrated circuit techniques supported on a suitable substrate. Four semi-conductor junctions are used which are a Peltier junction or a junction capable of emitting or absorbing heat, a light-emitting junction, a junction that generates electrical current when exposed to light and a temperature sensing junction. The circuit cooperates to control time and switch the current through the Peltier junction to heat and cool it. The light-emitting junction emits light onto the reflecting surface. The light sensing means senses the reflected light, and the Peltier junction selectively heats and cools the reflecting surface causing moisture to condense on the surface which changes the reflecting properties of the surface and changes the amount of light to the light sensing junction. Current through the Peltier junction is then switched causing the Peltier junction to heat the reflecting surface evaporating the moisture.

Abstract: A dew point hygrometer wherein separate reflective surfaces reflect light from separate light sources to a single light sensor. One surface is cooled to develop a coating of condensation. The other surface provides a standard to detect contamination build-up on both surfaces, and to detect variations in the operation of the single light sensor.