IN-CIRCUIT TESTING DEVICE

• Main Author: NAGANO KATSUMI
• Format: Patent
• Language: English
• Published: 05.10.1989
• Subjects: MEASURING; MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES; PHYSICS; TESTING

PURPOSE:To measure low resistance with high accuracy by supplying a measurement voltage to a resistance to be measured and a reference resistance and finding the parasitic resistance value that a measuring circuit has internally. CONSTITUTION:The resistance Rx to be measured and reference resistance R0 are mounted on a printed board PCB and probe pins CP1-CP4 of the testing device are pressed against test lands TL1-TL4 of the board PCB. Here, when relay contact points RLY1 and RLY2 are turned on, the electric power from a power source Vs for measurement is supplied to the resistance Rx through a parasitic resistance Rp1 and then a current I1 flows; and the current value of the parasitic resistance Rp2 is the sum of the contact resistance values of the contact points RLY1 and RLY2 and pins CP1 and CO2. Then when the contact points RLY1 and RLY2 are broken and relay contact points RLY3 and RLY4 are turned on, the electric power from the power source Vs is applied to the resistance R0 through the parasitic resistance Rp2 and a current I2 flows; and the value of the parasitic resistance Rp2 is the sum of the contact resistance values of the contact points RLY3 and RLY4 and pins CP3 and CP4. In those cases, the number of contacts included in the feeding path is equal, so it is considered that Rp1=Rp2, from which the values of the resistances Rp1 and Rp2 and resistance Rx are found.