An Enhanced Automatic Balancing Bridge and Its Method for Realizing Open-loop Compensation
An automatic balancing and enhanced technology, applied in the direction of the device where the measured value is automatically compared with the reference value, etc., can solve the problems of low measurement accuracy and slow measurement speed.
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Embodiment 1
[0064] like figure 2 As shown, the enhanced automatic balance bridge includes excitation source, DUT, voltmeter 1, voltmeter 2, range resistor, zero-crossing detection circuit, modulation-demodulation circuit, four-terminal pair interface and measurement cable. When the automatic balancing bridge does not reach a balanced state, the error current Id at the Lp end passes through the Lp end measurement cable → zero-crossing detection circuit → modulation-demodulation circuit → range resistance → Lc end measurement cable → Lp end measurement cable → ..., in turn cycle , forming a negative feedback loop LOOP.
[0065] like image 3 As shown, the zero-crossing detection circuit mainly includes an I / V conversion circuit, a signal amplification circuit, an AC coupling circuit, a D / A conversion circuit N1, a signal amplification and filtering circuit, and a balance state detection circuit. When the automatic balance bridge does not reach the equilibrium state and the error current ...
Embodiment 2
[0078] On the basis of above-mentioned embodiment 1, combine Figure 5 As shown, the present invention proposes an open-loop compensation method for an enhanced automatic balancing bridge. To make the automatic balancing bridge reach a balanced state quickly and accurately, it is necessary to disconnect the negative feedback loop of the enhanced automatic balancing bridge, and to open-loop The amplitude loss and phase offset of the state are calculated and compensated respectively. The specific execution process is as follows Image 6 shown.
[0079] Step 1: Execute the initialization of the enhanced automatic balancing bridge, mainly including DDS signal output, range resistance selection, amplitude gain selection, filter circuit selection, integration capacitor selection, switch state selection, etc.;
[0080] Step 2: switch S1 and switch S2 to point B respectively, connect the DC voltage sources DC1 and DC2, disconnect the negative feedback loop of the automatic balancing ...
Embodiment 3
[0091] On the basis of the above-mentioned embodiment 1 and embodiment 2, after the automatic balance bridge reaches a balanced state, the impedance measurement is started, combined with Figure 7 The schematic diagram of impedance measurement is shown, and the specific execution process is as follows Figure 8 shown.
[0092] Step 1: Turn the switch S5 to A to measure the voltage signal Vx;
[0093] Step 2: Turn the switch S5 to B to measure the voltage signal Vr;
[0094] Step 3: According to formula (1) described Calculate the impedance value Zx of the device under test, where Rr is the range resistance value, and all range resistances are standard resistances with high precision and low temperature drift.
[0095] The present invention proposes an enhanced automatic balance bridge and its method for realizing open-loop compensation. It adopts a negative feedback loop composed of a zero-crossing detection circuit, a modulation-demodulation circuit, and a range resistor,...
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