title: An analog-digital feedback system for measuring photoreceptor properties with an equal response method.
abstract: This paper describes a feedback system in which a neutral density wedge automatically controls the light flux applied to a photoreceptor, so that an intracellular recorded response is held constant. We describe here a "differential sampler" that subtracts the photoreceptors dark response from the light response induced by a chopped light source. The resulting signal drives the feedback system. The response time of the feedback system can be adjusted with a "digital integrator" to match a range of variable conditions that occur in different experiments.
mesh_terms: D000818:Animals; D004175:Diptera / Q000502:physiology*; D004594:Electrophysiology; D005246:Feedback; D010775:Photic Stimulation / Q000295:instrumentation*; D010786:Photoreceptor Cells / Q000502:physiology*