Electronic reciprocator for well logging systems including photoelectric feedback means

Claim 1

IN THE WALL LOGGING SYSTEM HAVING A D.C. SIGNAL VARYING WITH FORMATION PARAMETERS, MEANS FOR CONVERTING SAID VARYING D.C. SIGNAL TO AN ALTERNATING CURRENT SIGNAL, MEANS TO SUPPLY SAID ALTERNATING CURRENT SIGNAL TO A PHOTOCONDUCTIVE RESISTOR NETWORK, COMPRISED OF A FIXED RESISTOR, A PHOTOCONDUCTIVE RESISTOR IN SERIES THEREWITH AND A LIGHT SOURCE IN FIXED RELATION TO THE PHOTOSENSITIVE RESISTOR SO AS TO VARY RESISTANCE OF THE PHOTOSENSITIVE RESISTOR INVERSELY WITH INTENSITY OF THE LIGHT SOURCE, MEANS CONNECTED TO THE OUTPUT OF SAID PHOTOCONDUCTIVE RESISTOR NETWORK TO SUPPLY A VOLTAGE VARYING IN AMPLITUDE RELATIVE TO THE VOLTAGE AT THE OUTPUT OF THE PHOTOCONDUCTIVE RESISTOR NETWORK TO THE RIGHT SOURCE SO THAT UPON CHANGE IN SUCH OUTPUT VOLTAGE THERE WILL BE A CHANGE IN INTENSITY OF THE LIGHT SOURCE AND CORRESPONDINGLY A CHANGE IN RESISTANCE OF THE PHOTO-SENSITIVE RESISTOR TO BRING THE NETWORK BACK INTO BALANCE TO MAINTIAN AN APPROXIMATELY CONSTANT OUTPUT VOLTAGE, A STABLE D.C. VOLTAGE SOURCE SUPPLYING A CONSTANT D.C. VOLTAGE PHOTOCONDUCTIVE RESISTOR NETWORK,AND MEANS INDICATING THE D.C. POTENTIAL ACROSS THE PHOTOCONDUCTIVE ELEMENT WHICH POTENTIAL IS PROPORTIONAL TO THE RECIPROCAL OF THE VARYING D.C. INPUT SIGNAL.