Abstract: The presence of an undesirable quantity of noncondensible gases in a refrigeration unit is inferred as a function of both the vapor pressure and temperature at a selected point in the refrigeration unit where the noncondensible gases tend to gather. Purging of these noncondensible gases, which contaminate the refrigerant, is responsive to a comparison in a programmable controller of the actual vapor pressure measured at the selected point, and the known pressure of uncontaminated refrigerant at the temperature existing at the selected point. On detecting a difference between these pressures that is greater than a desired value, the controller calculates a control output signal needed to purge a volume of contaminated vapor from the unit that is effective for reducing the difference between the measured pressure of contaminated refrigerant and the known pressure of uncontaminated refrigerant to a desired value.

Abstract: A method and apparatus for detecting the presence of a liquid level at a monitor point along the depth of a borehole utilizes a diaphragm pressure switch for sensing the pressure of a captive air column in a measurement tube extending from the pressure switch to a predetermined point below the monitor point. In use, a rising liquid level in the borehole seals off the open lower end of the measurement tube from the earth atmosphere and allows the rising liquid level to compress the captive air column. In a preferred embodiment a visual signal is activated by the pressure switch when the rising liquid level in the borehole reaches the monitor point.

Abstract: A method for detecting the presence of a liquid level at a monitor point along the depth of a borehole utilizes a diaphragm pressure switch for sensing the pressure of a captive air column in a measurement tube extending from the pressure switch to a predetermined point below the monitor point. In use a rising liquid level in the borehole seals an open lower end of the measurement tube from the earth atmosphere and allows the rising liquid level to compress the captive air column. In a preferred embodiment a visual signal is activated by the pressure switch when the liquid level in the borehole reaches the monitor point.