Controlled multidigit resistance box - has control unit for selecting desired combination of resistors and connected to switching elements of each digit

摘要

The controlled multidigit resistance box comprises digits each comprising "n" series-connected resistors, an operational amplifier and two switching elements connected to each lead of each resistor. One of the switching elements is connected to the inverting input of the operational amplifier, while the other is connected to the output of the operational amplifier. The resistance box further includes a control unit for selecting a desired combination of resistors, connected to the switching elements of each digit. The centre tap of power sources of the operational amplifier of the previous digit is connected to the input of the next digit of the resistance box.