Filter regulator for microspectrophotometer

In a device for setting a graduated interference filter of a microspectrophotometer having an electrically operable adjustment means controlled by a graduated control knob (8) for setting the filter to a chosen wavelength, the improvement comprising a first drive motor (M.sub.1) operably connected to the filter, a first follower control circuit including a first differential amplifier (V.sub.1) having an output connected to the drive motor, an input (6) of the first differential amplifier being connected to a signal generator (P.sub.1) responsive to movement of the interference filter and another input (7) connected to a nominal signal generator (P.sub.2) responsive to movement of the control knob, a second drive motor (M.sub.2) selectively connectable to said control knob (8), a second follower control circuit including a second differential amplifier (V.sub.2), one input of the second amplifier (V.sub.2) being connected to said nominal signal generator (P.sub.2), another input of the second amplifier (V.sub.2) being selectively connectable to one of a plurality of adjustable signal generators (P.sub.A, P.sub.B . . . P.sub.N), an output of said second amplifier being operably connected to said second drive motor (M.sub.2) whereby one of a plurality of predetermined settings of said filter can be chosen by activating one of said adjustable signal generators and other settings of said filter can be chosen by manually moving control knob (8).