Abstract: An apparatus for selecting a centrifugal fluid machine according to the present invention can easily select a centrifugal fluid machine having a required performance from among a plurality of centrifugal fluid machines having an order of priority. The apparatus (1) for selecting a centrifugal fluid machine comprises an input device (12) for inputting required performance data for a centrifugal fluid machine and a storage device (16) for storing data (162) regarding respective performance ranges and selection priorities (163) for the respective centrifugal fluid machines.

Abstract: A computer-implemented method of calculating various types of characteristic curves of a centrifugal fluid machine according to the present invention can easily calculate a Q-H characteristic curve, a Q-E characteristic curve, a Q-NPSH characteristic curve, or the like. The method of calculating various types of characteristic curves uses two prescribed characteristic curves Y1=a11+a12x+a13x2+ . . . +a1nx(n−1) and Y2=a21+a22x+a23x2+ . . . +a2nx(n−1) formed of high-order equations for a centrifugal fluid machine to calculate a characteristic curve Y3=b1+b2x+b3x2+ . . . +bnx(n−1) formed of a high-order equation which passes through different coordinates (x3, y3).

Abstract: A computer-implemented method of calculating various types of characteristic curves of a centrifugal fluid machine according to the present invention can easily calculate a Q-H characteristic curve, a Q-E characteristic curve, a Q-NPSH characteristic curve, or the like. The method of calculating various types of characteristic curves uses two prescribed characteristic curves Y1=a11+a12x+a13x2+ . . . +a1nx(n−1) and Y2=a21+a22x+a23x2+ . . . +a2nx(n−1) formed of high-order equations for a centrifugal fluid machine to calculate a characteristic curve Y3=b1+b2x+b3x2+ . . . +bnx(n−1) formed of a high-order equation which passes through different coordinates (x3, y3).

Abstract: An apparatus for selecting a centrifugal fluid machine according to the present invention can easily select a centrifugal fluid machine having a required performance from among a plurality of centrifugal fluid machines having an order of priority. The apparatus (1) for selecting a centrifugal fluid machine comprises an input device (12) for inputting required performance data for a centrifugal fluid machine and a storage device (16) for storing data (162) regarding respective performance ranges and selection priorities (163) for the respective centrifugal fluid machines.

Abstract: A modem detects the received signal level at the start of communication and inserts an attenuator in the received input circuit if the level is too high. This arrangement extends the dynamic range of the modem without requiring a complex demodulating circuit.