| 摘要 |
The proposed conductometric moisture meter for materials, specifically plastic and viscous materials contains a conductometric sensor with two needle electrodes, isolating capacitors, switches, a differential amplifier designed according to a circuit with two operational amplifiers, two high-frequency signal amplifiers, a multiplier, an automatic switch, a low-frequency selective amplifier, two low-pass filters, a metering unit, and additionally, a low-frequency signal generator, two phase-sensitive rectifiers, the second low-frequency selective amplifier, a voltage divider, the second measuring unit, an additional operating amplifier, a feedback resistor, and an integrator. The electrodes are connected to the inputs of the differential amplifier via the capacitors and the switches. The outputs of the operational amplifiers in the circuit of the differential amplifier are accordingly connected to the inputs of the high-frequency signal amplifiers. The output of the first amplifier is connected to the first input of the multiplier. The noninverting output and the inverting output of the second amplifier are connected to the second input of the multiplier via the automatic switch. The input of the integrator is connected to the output of the multiplier, and the output is connected to the control input of the switch in the circuit of the first electrode. The inverting input of theadditional operating amplifier is connected to the output of the circuit of the second electrode, and the output is connected to the inverting input of the additional operating amplifier, via the feedback resistor, and the input of the first selective amplifier. The output of the first selective amplifier is connected to the input of the first filter via the first phase-sensitive rectifier. The first measuring unit is connected to the input of the first filter. The second input of the divider is connected to the output of the second filter. The input of the second filter is connected to the output of the second selective amplifier via the second phase-sensitive rectifier. The input of the second selective amplifier is connected to the output of the integrator. The control inputs of the phase-sensitive rectifiers and the automatic switch are connected to the output of the low-frequency signal generator. The second measuring unit is connected to the output of the divider. The proposed moisture meter is distinctive by its enhanced measurement accuracy due to the exclusion of temperature errors.
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