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公开(公告)号：DE68926296T2
公开(公告)日：1996-11-21
申请号：DE68926296
申请日：1989-06-08
Applicant: ROSEMOUNT INC
Inventor： SCHULTE JOHN , ORTH KELLY , FRICK ROGER , WESTFIELD BRIAN , PASCHKE RANDY
Abstract: A charge balanced feedback type transmitter generates charge packets representative of a sensed parameter. Improved performance is achieved by the additiion of resistance connected between a charge packet generating reactance and an integrator to reduce the effects of noise caused by switching transients and by ground noise which is coupled to the charge packet generating circuitry by stray capacitance. The charge packets are integrated by the integrater, and the integrator output is supplied from a selective basis to the input of a comparator. The output of the comparator is used to control the application of charge packets to the integrator to achieve charge balance. The input of the comparator is selectively connected to the output of the integrator, to a first supply voltage, or to a second supply voltage to ensure a stable output of the comparator at a critical time when charge is being supplied to the integrator.
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公开(公告)号：DE69222652D1
公开(公告)日：1997-11-13
申请号：DE69222652
申请日：1992-08-20
Applicant: ROSEMOUNT INC
Inventor： ANDERSON STEPHEN D , FRICK ROGER , MONZO GLEN , WESTFIELD BRIAN
Abstract: A three wire transmitter bidirectionally communicates AC signals to and from a first external device and sends DC signals to a second external device. The transmitter includes a communication circuit which is energized from power and common terminals and includes memory storage for transmitter status and a process variable (PV). The communication circuit receives a sensor output indicative of the PV and provides the DC signal and the AC signal to a signal terminal which connects to both external devices, and also receives AC signals from the first external device. The communications circuit has a characteristic AC impedance between the signal and common terminals over an AC frequency range for receiving and transmitting AC signals to and from the first external device so that the receiving signals are not shorted out and so the transmitted signals can be received. The communications circuit has a characteristic DC impedance between the signal and common terminals over a range of frequencies which include DC and typically extend to approximately 20 Hz. The characteristic impedance is substantially lower than the impedance of the second external device which receives DC signals so that the accuracy of the DC signal is not compromised.
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公开(公告)号：DE68926296D1
公开(公告)日：1996-05-23
申请号：DE68926296
申请日：1989-06-08
Applicant: ROSEMOUNT INC
Inventor： SCHULTE JOHN , ORTH KELLY , FRICK ROGER , WESTFIELD BRIAN , PASCHKE RANDY
Abstract: A charge balanced feedback type transmitter generates charge packets representative of a sensed parameter. Improved performance is achieved by the additiion of resistance connected between a charge packet generating reactance and an integrator to reduce the effects of noise caused by switching transients and by ground noise which is coupled to the charge packet generating circuitry by stray capacitance. The charge packets are integrated by the integrater, and the integrator output is supplied from a selective basis to the input of a comparator. The output of the comparator is used to control the application of charge packets to the integrator to achieve charge balance. The input of the comparator is selectively connected to the output of the integrator, to a first supply voltage, or to a second supply voltage to ensure a stable output of the comparator at a critical time when charge is being supplied to the integrator.
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