Solution concentration responsive apparatus

摘要: Apparatus yeilding an electrical signal representative of the position a boundary line between adjacent light and dark zones, with respect to reference position, comprises two photoelectric cells having separation in direction which moves. Means are provided whereby output P1 that one photocells is last reached by during its movement multiplied constant k, yielding K.P1 which, together P2 from other photocell, applied difference amplifier providing passes through zero when = P2. This may be input second amplifier, receiving also third differential negative whenever less than predetermined value. The final control traversal assembly including photocells, so as obtain measure displacement.