Elster Instromet 2000, Instruction Manual

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Model 2000 Flow Computer Instruction Manual
1.0 INTRODUCTION
Model 2000 issue 21 Page No
1
1. INTRODUCTION
The INSTROMET Model 2000 Flow Computer is designed to calculate the total energy, volume and instantaneous flow rates
of gas and alternatively Liquids. Calculation is carried out using inputs from pulse generating turbine meters or from
ultrasonic gas meters or from differential pressure measurement across orifice plates together with temperature sensors and
transmitters for line pressure. The Model 2000 uses pre-set or active input values of relative density, gas composition data
and heating value, active values can be received directly from a gas chromatograph or can be written serially from a
supervisory system.
The flow of gas is calculated using gas compressibility (Z factor) methods selected from a list of which includes AGA 8, ISO
12213 and AGA 3 NX19 as well as fixed factors for certain applications. As an alternative the flow of gas can be calculated
using a transducer input for line density.
The flow of liquid is calculated using fixed or measured factors for density and relative density and correction based upon
measured temperature and pressure of the Liquid in accordance with API standard chapters 11.2.1M, 11.2.2M & 12.
The Model 2000 has the facility of both high and low alarms on all active input signals, the alarms can be selected to enable
a default value to be used in flow calculation for the parameter in the alarm condition. Indication is given of the time of
occurrence and clearance of the alarm state, alarm output signals are also provided.
A feature of the Model 2000 is that it can use digital communication to the differential pressure, pressure and temperature
transmitters using the HART protocol eliminating the need for calibration of the Model 2000. This feature also eliminates the
errors in flow measurement due to ambient temperature effects on the Model 2000, only the temperature coefficient of the
transmitters contribute to the error.
As an alternative the Model 2000 can be operated from transmitters that supply a 4–20mA current output and also direct
from a 100 ohm platinum resistance thermometer for temperature measurement, these types of input are measured using
analogue inputs and a high resolution A-D converter. The analogue inputs are calibrated using software.
The Model 2000 has two RS232/RS485 serial data outputs which can provide Modbus RTU or ASCII communication
protocol for operation with system devices and a serial ASCII protocol compatible with most printers.
To provide maximum security of operating data and flow measurement while maintaining flexibility with the auxiliary
functions, the Model 2000 is provided with an edit facility where selected data can be changed while security can be
preserved with critical data.
All input and output signals are tested to ensure that they are within the designed operating limits, an alarm display records
the time when alarms occur and clear. During an alarm condition the total flows can be selected to be displayed on separate
counters.