Programmable control precision resistor box

Abstract

The invention relates to a programmable control precision resistor box which comprises a controller, a DA (digital to analog) converter, a current sampling circuit and an operational amplifier, wherein an output end of the controller is connected with a digital input port (Di end) of the DA converter; an output end of the current sampling circuit is connected with a Vref end of the DA converter; a voltage output end (Vout end) of the DA converter is connected with a '+' end of the operational amplifier; an output end of the operational amplifier is connected with a '-' end; a load is connected between the output end of the operational amplifier and the output end of the current sampling circuit. According to the programmable control precision resistor box, the circuit is simple, multiple mechanical switches and precision resistors are not required, and the production cost is very low; only one high-precision current sampling resistor is required to simulate one resistor through controlling of the DA converter, and the resistor has a wide range and high precision; if a multiplication type DA converter is adopted, the DA converter can be used for AC/DC (alternating current/direct current) occasions; with the adoption of the programmable control method, the resistor box is conveniently connected with a computer to form an automatic testing system.

Description

technical field [0001] The invention relates to a program-controlled precision resistance box, which uses a DA converter, an operational amplifier and a controller to complete the control of the precision resistance. Background technique [0002] Resistance boxes are widely used in circuit debugging and testing. At present, the resistance box used is to connect dozens of precision resistors properly, and then use a multi-position rotary switch to select the resistance value required by the circuit; there are also several relays controlled by a single-chip microcomputer instead of the above-mentioned multi-position rotary switch to realize the so-called Program-controlled resistance boxes, because these resistance boxes use mechanical switches or relays, their contacts will wear and age after long-term use, resulting in increased contact resistance, which greatly reduces the accuracy of the resistance box; and the production of high-performance resistance boxes requires a lot...

AI Technical Summary

Problems solved by technology

At present, the resistance box used is to connect dozens of precision resistors properly, and then use a multi-position rotary switch to select the resistance value required by the circuit; there are also several relays controlled by a single-chip microcomputer instead of the above-mentioned multi-position rotary switch to realize the so-called Program-controlled resistance boxes, because these resistance boxes use mechanical switches or relays, their contacts will wear and age after long-term use, resulting in increased contact resistance, which greatly reduces the accuracy of the resistance box; and the production of high-performance resistance boxes requires a lot of High-precision, low temperature coefficient resistors, these resistors are expensive and difficult to obtain

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