OIL CONCENTRATION DETECTION SYSTEM

To improve accuracy of a measurement value of a concentration of a refrigeration machine oil by using an oil concentration sensor provided in a compressor.SOLUTION: A concentration detection system (1) includes: an oil concentration sensor (55) disposed in fluid containing a refrigerant and refrigeration machine oil in a compressor (10); a measurement section (101) determining a first index indicating a concentration of the refrigeration machine oil on the basis of a predetermined relational expression indicating a relation between a detection value obtained by the oil concentration sensor (55) and the oil concentration of the refrigeration machine oil; and a correction section (102) determining a second index that is a saturated concentration of the refrigeration machine oil when the refrigerant is in the superheated state and correcting the predetermined relational expression on the basis of a difference between the first index and the second index at a same superheating degree. The correction section (102) corrects the first index on the basis of the corrected predetermined relational expression.SELECTED DRAWING: Figure 5 【課題】圧縮機内に設けられる油濃度センサによる冷凍機油の濃度の測定値の精度を向上させる。【解決手段】濃度検出システム（1）は、圧縮機（10）内の冷媒と冷凍機油とを含む流体中に配置される油濃度センサ（55）と、油濃度センサ（55）の検出値と、冷凍機油の油濃度との関係を示す所定の関係式に基づいて、冷凍機油の濃度を示す第１指標を求める測定部（101）と、冷媒が過熱状態であるときの冷凍機油の飽和濃度を示す第２指標を求めると共に、同一の過熱度における第１指標と第２指標との差に基づいて所定の関係式を補正する補正部（102）とを備え、補正部（102）は、補正された所定の関係式に基づいて、第１指標を補正する。【選択図】図５