# US 4,392,044 A · Method for detecting whether dissimilar metals are being welded > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,392,044 A - Document ID: US4392044A - Status: Granted - Kind: A - Application number: 06/251,767 - Filed: 1981-04-07 - Granted: 1983-07-05 - Earliest claimed: 1981-04-07 - Assignees: Amax Inc. - Inventors: Teh P. Wang; Elmer J. Korn - Web page: https://patentgrep.com/patent/US4392044A ## CPC - G01N 27/002: {by investigating the work function voltage} - G01R 19/00: Arrangements for measuring currents or voltages or for indicating presence or sign thereof (G01R5/00 takes precedence; for measuring bioelectric currents or voltages A61B5/24) - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract A method for detecting whether dissimilar metals or alloys are being welded together is disclosed. Metals or alloys are welded together and electrical leads connected to a multi-purpose potentiometer or a voltmeter contact each metal at points heat conductively remote from the weld. The arrangement performs as a thermocouple with the weld acting as the "hot junction" and the contact points remote from the weld being at substantially ambient temperature, and acting as the "cold junction." According to the thermoelectric laws, if the metals are dissimilar, a current and EMF result provided that the hot junction and the cold junction are at different temperatures. If the metals are similar, no signal is generated. The potentiometer or the voltmeter detects whether any electrical signal is present. In the same manner, an unknown metal may be positively identified by welding it to different reference metals until no signal is generated. ## Claims ### Claim 1 A method for detecting whether two dissimilar metals are being welded together comprising the steps of: a. placing in juxtaposition the edges of two metals that are to be welded together; b. joining said metals by welding; c. contacting said metals with electrical leads which are electrically connected to a voltage or current sensing device at points heat conductively remote from the weld, while said weld is hot; and d. detecting whether an electrical signal is present, to reveal the similarity or dissimilarity of said metals. ### Claim 2 A method for detecting whether two dissimilar metals are being welded together comprising the steps of: a. placing in juxtaposition the edges of two metals that are to welded together; b. contacting said metals at points heat conductively remote from where they are to be welded with electrical leads which are electrically connected to a voltage or current sensing device; c. joining said metals by welding; and d. detecting whether an electrical signal is present, to reveal the similarity or dissimilarity of said metals. ### Claim 3 A method for welding substantially identical metals together comprising the steps of: a. placing in juxtaposition the edges of two metals that are to be welded together; b. joining said metals by welding; c. contacting said metals with electrical leads which are electrically connected to a voltage or current sensing device at points heat conductively remote from the weld, while said weld is hot; d. detecting whether an electrical signal is present, to reveal the similarity or dissimilarity of said metals; and e. dressing the weld if no signal, or a negligible signal is present. ### Claim 4 A method for welding substantially identical metals together comprising the steps of: a. placing in juxtaposition the edges of two metals that are to be welded together; b. contacting said metals at points heat conductively remote from where they are to be welded with electrical leads which are electrically connected to a voltage or current sensing device; c. joining said metals by welding; d. detecting whether an electrical signal is present to reveal the similarity or dissimilarity of said metals; and e. dressing the weld if no signal, or a negligible signal is present. ### Claim 5 (depends on 1, 2) A method for detecting whether two dissimilar metals are being welded together, as recited in claims 1 or 2, wherein: said electrical leads contact said metals at points approximately one foot or more from the weld. ### Claim 6 (depends on 5) A method for detecting whether two dissimilar metals are being welded together, as recited in claim 5, wherein: said electrical leads are copper wires; and said metals are metal coils. ### Claim 7 (depends on 6) A method for detecting whether two dissimilar metals are being welded together, as recited in claim 6, wherein: said electrical leads have conductive clamps attached to their ends for contacting said metals; and said electrical signal is detected by a voltmeter, ammeter, or potentiometer. ### Claim 8 (depends on 1) A method for detecting whether two dissimilar metals are being welded together, as recited in claim 1, wherein: said contact between said electrical leads and said metals occurs within approximately 15 seconds of said welding. ### Claim 9 (depends on 2) A method for detecting whether two dissimilar metals are being welded together, as recited in claim 2, wherein: said metals are welded by an electric welder; one of said electrical leads is broken by a switch; and said electrical signal is detected by a voltmeter, ammeter, or potentiometer. ### Claim 10 (depends on 1) A method for detecting whether two dissimilar metals are being welded together, as recited in claim 1, further comprising: e. before step a., arranging the metals on a welder; and f. after step b., but before step c., quickly removing the welded section from said welder and clamping it firmly on a non-conductive clamp, with the weld approximately at the center. ### Claim 11 (depends on 9) A method for detecting whether two dissimilar metals are being welded together, as recited in claim 9 further comprising: e. before step a., arranging the metals on an electric welder; f. before step c., placing said switch in an open position, thereby insulating a direct current circuit containing said voltmeter from an alternating current circuit containing said electric welder; and g. immediately after step c., and before step d., closing off and breaking said alternating circuit, and placing said switch in a closed position to complete said direct current circuit. ### Claim 12 (depends on 1, 2) A method for detecting whether two dissimilar metals are being welded together, as recited in claims 1 or 2, for the positive identification of one of the metals, where the other metal is a known reference metal, further comprising: e. cutting off said weld if a signal is generated; f. replacing said known reference metal with another known reference metal; and g. repeating steps a. through f. until no electrical signal is detected during step d.