Vaisala Oy

Vaisala Oyj

Matti Lyyra

Lars Stormbom

Jukka Leppänen

Jukka Lepp&auml;nen

The invention relates to a method and apparatus for measurement of total water content in a liquid. According to the method, the relative water content (aw) of the liquid is measured in a first measurement step at a first temperature (T). According to the invention, the temperature of the liquid under measurement is altered from the first temperature (T) and the relative water content is measured in a second measurement step at the second, altered temperature (T), whereby, based on these at least two measurement values (aw()T, aw()T), the total water content is determined from the temperature dependence of water dissolution into the liquid under measurement.

Method and apparatus for defining water content of a liquid

A method and apparatus for measuring the water content of a liquid, including a method step for electrically measuring the property of the liquid for one parameter. The properties of the liquid are measured at least substantially simultaneously by another electrical method, where the properties of the liquid are measured using both a relative-value and an absolute-value measurement method.

Method and apparatus for measuring water content

The invention relates to an indirect measurement method of dewpoint or gas concentration and an apparatus suited for prediction of icing. The method is based on measuring the relative concentration of the gas directly and simultaneously measuring the temperature of the element (3) measuring the relative concentration of the gas. According to the invention, the temperature of the relative value measuring element (3) is shifted so as to bring the operation of the measuring element to a measurement range of maximally high sensitivity.

Method of measuring dewpoint or gas concentration and apparatus for

A third reference capacitor cooperates with first and second reference capacitors to minimize measurement errors in a measurement circuit of the type in which reference and measurement capacitors are connected, one at a time, to an oscillator of the measurement circuit to generate an output frequency proportional to the capacitance of the capacitor being measured. The measurement errors introduced by different temperature and loading conditions during calibration and measurement modes of the measurement circuit are minimized.

Method of and arrangement for accurately measuring low capacitances

Method of and arrangement for measuring low capacitances include generating a periodic frequency signal having time periods of duration dependent on capacitance, and alternately connecting an unknown capacitance to be measured and a known reference capacitance, one after the other, to a frequency generator for an equal number of time periods of the frequency signal. Each time period has a first and a second time interval proportional to the reference capacitance and the unknown capacitance, respectively. A DC voltage output signal proportional to the unknown capacitance being measured is generated in response to the durations of the first and second time intervals. The DC voltage output signal is preferably scaled, linearized and temperature compensated.

Method of and arrangement for measuring low capacitances

A method of and arrangement for measuring impedances, particularly low capacitances, by alternately connecting one or more reference impedances and sensor impedances to a measuring circuit. A programmed memory is used to take into account the individual non-linearities of the impedance sensor(s) and, optionally, to compensate variations of ambient circumstances such as temperature.

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Vantaa, Finland

Matti Lyyra