Circuit for measuring grounding resistance or current with high precision by using electronic scale chip
By building a common mode voltage on the electronic scale chip, the problem that the electronic scale chip is difficult to measure ground resistance or current with high accuracy is solved, and 24-bit high-precision current/resistance measurement is achieved, and the circuit is simple and cost-effective.
Patent Information
- Application Number
- CN202420868606.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-24
- Publication Date
- 2025-02-11
- Estimated Expiration
- 2034-04-24
AI Technical Summary
It is difficult to use electronic chips to measure ground resistance or current with high accuracy, mainly because the positive and negative input terminals of the electronic chip must be higher than their common mode voltage to operate in a linear range with high accuracy.
By using a negative voltage with a value greater than the minimum common mode voltage of the electronic chip, it generates and applies to the REFN, AGND, and DGND pins of the chip, thereby building a common mode voltage so that the electronic chip can be used at the positive input and negative input. These reference voltages work between them, enabling high-precision current/resistance measurements.
It realizes high-precision measurement of ground resistance or current on conventional electronic chips. The pre-amplification inside the chip is accurately corrected, and the measurement deviation is small after interchange, the circuit is simple, the cost is low, and the cost performance is relatively high.
Smart Images
Figure CN222461566U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of electronic measurement, in particular to a circuit for measuring grounding resistance or current with high precision by using an electronic scale chip, and is suitable for measuring electronic equipment using a single-chip microprocessor. Background Art
[0002] High-precision measurement of ground resistance and current is important for ensuring the safe operation of electrical and electronic equipment and related circuits. However, to achieve high-precision measurement of ground resistance, it is usually necessary to use more expensive professional testers.
[0003] Although electronic scale chips are cheap and available in large quantities, they are designed specifically for measuring bridge sensors and cannot measure ground resistance or current. The main reason is that the positive and negative input terminals of the electronic scale chip must be higher than the common mode voltage of the electronic scale chip to operate in a high-precision linear range. Summary of the invention
[0004] The utility model aims to provide a circuit for measuring ground resistance or current with high precision by using an electronic scale chip for an electronic device using a single-chip microprocessor.
[0005] The principle of the utility model is: using a negative voltage whose value is greater than the minimum common-mode voltage of the electronic scale chip, the negative voltage can be generated by a DC-DC circuit, or obtained by a dedicated integrated circuit, and connected to the REFN, AGND, and DGND pins of the electronic scale chip, a common-mode voltage can be constructed between the positive ANP input terminal and the negative ANN input terminal and REFN, AGND, and DGND. After such processing, the electronic scale chip can perform high-precision current / resistance measurement of the grounding resistance.
[0006] The circuit structure of the utility model is:
[0007] An electronic scale chip in which REFN, AGND, and DGND are sealed as GND inside the chip;
[0008] The REFP, AVDD and DVDD terminals of the electronic scale chip IC1 are connected to VCC, the GND terminal is connected to -0.7V to -1V, and the ANN terminal is grounded;
[0009] The DOUT terminal of IC1 is connected to the anode of diode D1, and the cathode of D1 is connected to the I port of the microprocessor. The cathode of D1 is also connected to ground through a fixed resistor R1.
[0010] The SCK terminal of IC1 is connected to the O port of the microprocessor;
[0011] For measuring the current to ground, the ANP terminal of IC1 receives the measuring current and one end of the fixed resistor RA, and the other end of RA is grounded.
[0012] For measuring resistance to ground, the ANP terminal of IC1 is connected to a high-performance constant current source and one end of the resistor to be measured RD, and the other end of RD is grounded;
[0013] The ANN end and the ANP end can be swapped;
[0014] The high-performance constant current source can output a stable constant current under a wide range of temperature changes, and the microprocessor is a single-chip microprocessor contained in the electronic device under test.
[0015] The method of measuring ground current using the above circuit is ( Figure 1 ): Let the current to be measured pass through RA to generate a voltage drop, and the electronic scale chip IC1 can convert it into 24Bist data. Replace the fixed resistor RA and let the electronic scale chip work in the linear period to measure the segmented current.
[0016] The method of measuring ground resistance using the above circuit is ( Figure 2 ): Use a high-performance constant current source, connect it to the resistor to be measured RD, and connect the other end of RD to ground, then the resistance value of the resistor RD can be measured with high accuracy.
[0017] The utility model uses a negative voltage to construct a common mode voltage on a conventional electronic scale chip, so that the electronic scale chip can directly operate on the ground resistance and work in a linear region, thereby obtaining 24-bit high-precision current / resistance measurement. The utility model has the advantages that the pre-amplification (32 times, 64 times, 128 times, 256 times) inside the electronic scale chip has been accurately calibrated, the measurement deviation is very small after the chip is interchanged, the circuit is simple, the cost is low, and the cost performance is high. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 This is the electrical schematic diagram of Example 1.
[0019] Figure 2 This is the electrical schematic diagram of Example 2. DETAILED DESCRIPTION
[0020] Example 1: Ground current measurement of electronic detonator initiator ( Figure 1 ).
[0021] IC1 = electronic scale chip HX71708, VCC = 3.3V, negative voltage is -1V, D1 = 1N4148, R1 = 10K, VREF, AGND, DGND are sealed as GND inside the chip.
[0022] The current to be measured is connected to the resistor RA, and the other end of RA is grounded. When RA = 0.05 ohm resistance, the maximum measurable current is 250mA. When RA = 0.25 ohm resistance, the current of μA level can be accurately measured.
[0023] The single-chip microprocessor is msp430fr2355.
[0024] Example 2: Ground resistance measurement of electronic detonator bridge wire ( Figure 2 ).
[0025] IC1 = electronic scale chip HX71708, VCC = 3.3V, negative voltage is -1V, D1 = 1N4148, R1 = 10K, VREF, AGND, DGND are sealed as GND inside the chip.
[0026] A 250uA high-performance constant current source is connected to the bridge resistor RD, and the other end of RD is grounded. The measured resistance RD is 0 ohm to 50 ohm, the measurement resolution is 0.001 ohm, and the error is less than 0.01 ohm.
[0027] The single-chip microprocessor is msp430fr2355.
Claims
1. A circuit for measuring ground resistance or current with high precision using an electronic scale chip, characterized in that: The REFN, AGND, and DGND of the electronic scale chip are sealed together as GND inside the chip; The REFP, AVDD and DVDD terminals of the electronic scale chip IC1 are connected to VCC, the GND terminal is connected to -0.7V to -1V, and the ANN terminal is grounded; The DOUT terminal of IC1 is connected to the anode of diode D1, and the cathode of D1 is connected to the I port of the microprocessor. The cathode of D1 is also connected to ground through a fixed resistor R1. The SCK terminal of IC1 is connected to the O port of the microprocessor; For measuring the current to ground, the ANP terminal of IC1 receives the measuring current and one end of the fixed resistor RA, and the other end of RA is grounded. For measuring resistance to ground, the ANP terminal of IC1 is connected to a high-performance constant current source and one end of the resistor to be measured RD, and the other end of RD is grounded; The ANN end and the ANP end can be swapped; The high-performance constant current source can output a stable constant current under a wide range of temperature changes, and the microprocessor is a single-chip microprocessor contained in the electronic device under test.