Emerson 00809-0100-4514, 1154 manual FV Iref

Page 34

Rosemount 1154

Reference Manual

00809-0100-4514, Rev BA January 2008

OSCILLATOR

VOLTAGE REGULATOR

ZERO AND SPAN

ADJUSTMENTS

CURRENT CONTROL

CURRENT LIMIT

REVERSE POLARITY PROTECTION

The oscillator has a frequency determined by the capacitance of the sensing element and the inductance of the transformer windings.

The sensing element capacitance is variable. Therefore, the frequency is variable about a nominal value of 32 kHz.

An integrated circuit amplifier is used as a feedback control circuit and controls the oscillator drive voltage such that:

fV Iref

p – p = --------------------

C1 + C2

The transmitter uses a zener diode, transistor, and resistors to provide a constant voltage of 6.4 V dc for the reference and 7 V dc for the oscillator.

Zero adjustment components consist of a potentiometer and resistor that develop a separate adjustable current that sums with the sensor current. The coarse zero switch switches resistors into the circuit as needed.

Span adjustment is performed with a potentiometer which determines the amount of loop current which is sensed and fed back to the current control amplifier.

The current control amplifier consists of an integrated circuit, two transistors, and associated components. The IC reference voltage is established at the junction of a resistor network. The current control amplifier drives the current control to a level such that the current detector feeds back a signal equal to the sum of the zero current and the variable sensor current.

A current limiter prevents the output current from exceeding 30 mA in an overpressure condition.

A zener diode provides reverse polarity protection.

4-4

Image 34

Contents Rosemount Reference ManualImportant Notice -- Errata Rosemount 1154 Alphaline Nuclear Pressure Transmitter Return of Material Changes From June 1999 to January Revision StatusNew Old Changes Rosemount Table of Contents Specifications Reference Data Maintenance TroubleshootingSection TOC-3 TOC-4 Section Introduction Overview About the TransmitterRosemount Section Installation Overview General ConsiderationsMechanical Considerations Process ConnectionsRosemount Conduit Electrical ConsiderationsTransmitter Wiring Connections Procedures InstallationMechanical Pressure Dimension Range CodeLiquid Service ElectricalTransmitter Terminal Block Rosemount Section Calibration Span Adjustment Zero AdjustmentOverview Calibration Calibration Procedures Zero and Span AdjustmentZero and Span Adjustment Screws Linearity Adjustment Damping Adjustment Linearity and Damping AdjustmentRosemount Calculate zero adjustment correction in terms of pressure Rosemount Section Operation Overview Transmitter OperationΔ-Cell Linearity Adjustment DemodulatorFV Iref Maintenance Troubleshooting OverviewSafety Messages Test Terminals Board CheckoutSensing Module Checkout Disassembly Procedure Process Flange RemovalRosemount 1154 Parts List Part DescriptionReassembly Procedure Rosemount Process Flange Reassembly Symptom Potential Source Corrective Action Post Assembly TestsOn Next Check for adequate voltage to the transmitter Specifications and Reference Data Nuclear SpecificationsPerformance Specifications Range Code Overpressure Effect Range Code Static Pressure Zero Effect Functional SpecificationsRange Code Response Time Range Code Pressure Ranges 25 to 0-150 inH2O 0-6.22 to 0-37.3 kPaPhysical Specifications Range Code Overpressure LimitRosemount Ordering Information Rosemount 1154DP, 1154HP, and 1154GP Spare Parts Rosemount 1154DP 1154HP 1154GP Part Description Order NoFor use with existing N0026 transmitter only Spare Parts Shelf Life Important Notice Rosemount Current Control Current Limit Index-2 Page ¢00809-XXXX-XXXX ¤