Contrec 415 User manual

415-M-V3.2
GAS & STEAM
FLOW COMPUTER
MODEL 415
June 2017

415-M-V3.2

415-M-V3.2
CONTENTS
List of Symbols
1. Introduction 7
1.1 Model Number Designation 9
2. Specification 10
3. Operation 14
3.1 Front Panel Operation 14
3.2 Flow Equations for Gases 16
3.2.1 Ideal Gas Law 22
3.2.2 General Gas 24
3.2.3 Natural Gas 25
3.3 Steam Measurement 26
3.4 Filtering 31
3.5 Non-Linearity Correction 33
3.5.1 Digital Input Linearity Correction 33
3.5.2 Analog Input Linearity Correction 35
3.6 The Output Pulse 37
4. Options 39
4.1 The 4-20mA Output Option 39
4.1.1 Load Specification 40
4.1.2 Calculation 40
4.2 The RS232/422/485 Interface Option 43
4.2.1 Hardware 43
4.2.2 Multipoint Communication 44
4.2.3 Communication Protocol 46
4.3 Data Logging 48
4.4 The Relay Output Option 49

415-M-V3.2
5. Calibration 50
5.1 Programming Chart 52
5.2 Definitions 59
6. Input Circuits 62
6.1 Frequency Flow Input 62
6.2 Analog Inputs 67
6.3 Remote Switches (Model 415A Only) 70
7. Installation 71
7.1 General 71
7.2 Wiring Designations for the Mode 415 73
7.3 Ex 410 Enclosure Dimensions 75
Appendix 76
Properties of Selected Gases 76
Index 78

415-M-V3.2
List of Symbols Used in this Manual
Symbol Description SI Units US Units
A Normalised signal from the
flowmeter which will be 0 at
4mA and 1 at 20mA.
G Specific Gravity for Gas.
hBSpecific Enthalpy at Reference
Conditions.
kJ/kg kJ/kg
hFSpecific Enthalpy at Flow
Conditions.
kJ/kg kJ/kg
KFK-factor (pulses/unit) for a
frequency flowmeter.
pulses/m3pulses/ft3
N Timebase Constant with which the
flowrate is displayed and is:
1 for units/second
60 for units/minute
3600 for units/hour
86400 for units/day
ᴘBDensity at base conditions. kg/m3lbs/ft3
ᴘF Density at flow conditions. kg/m3lbs/ft3
ᴩB Pressure at base conditions. kPa (abs) psia
ᴘC Critical pressure of gas. kPa (abs) psia

415-M-V3.2
Symbol Description SI Units US Units
PFPressure at flow conditions. kPa (abs) psia
QEEnergy value of steam. MJ/day
MJ/hr
MJ/min
MJ/sec
BTU x 1000/day
BTU x 1000/hr
BTU x 1000/min
BTU x 1000/sec
QMMass Flowrate. kg/day
kg/hr
kg/min
kg/sec
lbs/day
lbs/hr
lbs/min
lbs/sec
QVB Volume Corrected Flowrate. m3/day
m3/hr
m3/min
m3/sec
ft3/day
ft3/hr
ft3/min
ft3/sec
Note: If the corrected flowrate is at standard base conditions,
then the flow will be in scm or scf (ie. standard cubic meters or
feet).
If the corrected flowrate is at normalised base conditions, then the
flow will be in Nm3(ie. Normalised cubic meters).
SMSpan (Mass Flowrate at 20mA). kg/day
kg/hr
kg/min
kg/sec
lbs/day
lbs/hr
lbs/min
lbs/sec
SVSpan for a volumetric flowmeter
(eg vortex).
m3/day
m3/hr
m3/min
m3/sec
ft3/day
ft3/hr
ft3/min
ft3/sec

415-M-V3.2
Symbol Description SI Units US Units
SVB Span (Volumetric Flowrate at
20mA) and at base conditions.
m3/day
m3/hr
m3/min
m3/sec
ft3/day
ft3/hr
ft3/min
ft3/sec
TBTemperature at base conditions. °K
(Kelvin)
°R
(Rankin)
TCCritical temperature of gas. °K °R
TFTemperature at flow conditions. °K °R
VB Specific Weight of Steam at
Reference Conditions.
dm3/kg dm3/kg
VF Specific Weight of Steam at Flow
Conditions.
dm3/kg dm3/kg
ZbCompressibility at base conditions.
ZFCompressibility at flow conditions.

415-M-V3.2

415-M-V3.2
1. INTRODUCTION
The Model 415 Gas Flow Computer incorporates compensation for gas
and vapours to the following equations:
1. Ideal Gas Law using temperature & pressure correction, but where
compressibility is ignored.
2. General Gases where compressibility is calculated using the
Redlich-Kwong1equation.
3. Natural Gas using NX-192equation for supercompressibility.
4. Steam Equations for both saturated and superheated steam. Mass
and energy flowrates are calculated using standard equations to
determine the specific weight and enthalpy of steam.
Inputs from a wide range of flowmeters are handled including vortex,
turbine, orifice plate, averaging pitot tubes, wedges, V-Cones and target
flowmeters. In addition, where two differential pressure transmitters are
used across an orifice (or similar device) to increase the measured
flowrange, both D.P. Transmitter inputs can be accepted into the Flow
Computer and scaled separately with automatic crossover.
Options include a 4-20mA re-transmission, high and low flow alarms and
an RS232/422/485 output. A unique feature available with the
RS232/422/485 output is the ability to print flowrates and totals at
programmable time intervals.
This enables the instrument to function as a data logger when used in
conjunction with a printer, or other storage device.
Two versions of the instrument are available, the Model 415R with direct
RTD input, and the 415A with a 4-20mA temperature input. Both accept a
4-20mA pressure input.
The Model 415 is designed to supersede the Models 405GS and 405ST.
1Redlich & Kwong. "An equation of State". Chem Rev, vol 44, p233, 1949.
2Par Research Project NX-19. "Extension of Range of Supercompressibility
Tables", American Gas Association, 1962.
Introduction 7

415-M-V3.2
This instrument conforms to the EMC-Directive of the Council of European
Communities 2014/30/EU, the LVD directive 2014/35/EU and the following
standards:
EN61326:2013 Electrical equipment for measurement, control
and laboratory use – EMC requirements : Residential,
Commercial & Light Industry Environment &
Industrial Environment.
EN61010:2010 Safety requirements for electrical equipment for
measurement, control, and laboratory use.
8 Introduction

415-M-V3.2
1.1 MODEL NUMBER DESIGNATION
The Model number of an instrument describes which input and output
options are installed and the AC mains voltage rating.
Model 415 R. 1 0 E C
C for Conformal Coating
E for 220/240 VAC
A for 110/120 VAC
D for DC Power Only
Temperature Options
R for RTD input 0 for no option
A for 4-20mA 1 for 4-20mA output
2 for RS232/422/485
3 for Relay option
4 for 4-20mA and relays
5 for RS232/422/485 and
relays
Mounting
1 for panel mounting
2 for field mounting
3 for explosionproof
The Model number of the instrument is displayed on first entering
the Calibration Mode (see Section 5).
Introduction 9

415-M-V3.2
2. SPECIFICATION
General
Display: Alphanumeric LCD display with
backlighting and 2 lines x 20
characters/line.
Each character 5.5mm high.
Keyboard: Sealed membrane keyboard with four keys.
Transducer Supply: 8-24VDC field adjustable, 65mA maximum.
Power Requirements: 14 to 28.0 VDC, 300mA typical.
AC mains - Set internally to 95 - 135 VAC
or 190 - 260 VAC.
Operating Temperature: 0 to 55°C.
Facia: Watertight to IP65 or Nema 3S.
Dimensions: 144mm (5.7") wide x 72mm (2.8") high x
188mm (7.4") deep.
Depth behind Panel: 139mm (5.5") x 67mm (2.6").
Frequency Input
Frequency Range: Minimum: 0.25Hz on Rate.
0Hz on Total.
Maximum: 10KHz.
Input Circuits: Will accept most sine logic and proximity
switch inputs (see section 6.1).
K-factor Range: 0.1000 to 999,999.
Non-Linear Correction: Up to 10 correction points.
10 Specification

415-M-V3.2
4-20mA Inputs
Inputs: Flow (2), pressure & temperature.
Input Impedance: 250 ohms.
Measurement Ranges: Pressure: 0kPa (abs) (0 psia) to 100,000 kPa
(10,000 psia).
Temp:-273°C (-459.4°F) to 1200°C (2192°F).
Accuracy: 0.05%.
Circuit: The 250 ohm resistors are connected to a
common signal ground (current sinking).
Span (Flow): 999,999.
RTD Input (Model 415R)
Temperature
Measurement Range: -100°C (-148°F) to 200°C (392°F),
Note: a wider temperature range can be
handled via a 4-20mA input.
Accuracy: 0.1°C
RTD Type: Platinum PT100.
Linearity: The non-linearity of the RTD is internally
compensated for.
Pressure Input
Type: Absolute or Gauge.
Span: The absolute or gauge pressure at both 4mA
and 20mA is programmable.
Atmospheric: If a gauge pressure sensor is used the
atmospheric pressure can be programmed.
4-20mA Output
Function: The flowrate selected as the Default display
is output on the 4-20mA output.
Resolution: 10 bits.
Accuracy: Better than 0.1%.
Maximum Load: 500 ohms internally powered.
950 ohms from 24 VDC.
Isolation: Output is isolated.
Specification 11

415-M-V3.2
Relay Output
Function: High and low flowrate alarms based on the
flowrate selected as the default display.
Maximum Switching Power: 1250VA.
Maximum Switching Voltage: 250 VAC, 30VDC.
Maximum Switching Current: 5 Amps.
RS232/422/485 Option
Type: Both RS232 & RS422/485 are provided.
Function: Printer and computer protocols are
programmable.
Output: Output is on request or at a programmable
time interval.
Baudrate: 300 to 9600.
Data Bits: 7 or 8.
Parity: None, Odd, Even.
Pulse Output
Function: The pulse output is scaled and outputs one
pulse each time the Default total
increments by one digit.
Pulse Width: 10mSec (negative going pulse).
Duty Cycle: Maximum of 49 pulses per second.
Output: An open collector transistor will sink 100mA
maximum.
Ideal Gas
Display: Corrected Volume (m3or ft3).
Mass (kg or lbs).
Temperature Range: -273°C (-450°F) to 800°C (1472°F).
(RTD has a more limited range.)
Pressure Range: 0 kPa abs (0 psia) to 100,000 kPa (10,000
psia).
12 Specification

415-M-V3.2
General Gas
Gases: Handles most gases for which the critical
temperature, pressure and SG are known.
Compressibility: Calculated using Redlich-Kwong equation.
Display: Corrected Volume (m3or ft3).
Mass (kg or lbs).
Temperature Range: -273°C (-450°F) to 800°C (1472°F).
(RTD has a more limited range.)
Pressure Range: 0 kPa abs (0 psia) to 100,000 kPa (10,000
psia).
Natural Gas
Calculations: Uses NX-19 equation to calculate
supercompressibility Fpv.
Displays: Corrected Volume (m3or ft3).
Mass (kg or lbs).
Temperature Range: -40°C (-40°F) to 115°C (240°F).
Pressure Range: 101.325 kPa (14.69 psia) to 34,380 kPa
(4985 psia).
SG Range: 0.554 to 1.000.
Carbon Dioxide: 0 to 15% mole.
Nitrogen: 0 to 15% mole.
Steam
Displays: Mass (kg or lbs)
Energy (MJ or BTU x 1000).
Calculations: Uses 1967 IFC Formulation equations to
calculate specific weight and enthalpy of
steam.
Steam Type: Saturated and Superheated.
Temperature Range: 20°C (68°F) to 800°C (1472°F).
(RTD has a more limited range.)
Pressure Range: 1 kPa (abs) (1 psia) to 100,000 kPa (10,000
psia).
Specification 13

415-M-V3.2
3. OPERATION
The Model 415 uses a low power CMOS microprocessor to perform
all measurement and control functions.
The instrument is fully programmable with all operating parameters
and calculation constants user programmable (see Section 5 entitled
Calibration for information on programming). All parameters and
constants are stored in a non-volatile memory which retains data
without battery backup for a minimum of 10 years.
3.1 FRONT PANEL OPERATION
The alphanumeric display provides a clear indication of which parameter
is displayed and the engineering units.
During Calibration, the value which is to be normally displayed can
be programmed as the DEFAULT display. For example, if Mass is
required and is programmed as the DEFAULT display, then pressing
the RATE key will show the Mass flowrate, and pressing the TOTAL
key will show the Mass total.
The scaled pulse out, 4-20mA output option and high/low alarm option are
also based on the DEFAULT display selection. For example, the 4-20mA
output would be a re-transmission of the Mass flowrate, if the DEFAULT
display is set to Mass.
The DISPLAY key can be used to step through the data which can be displayed,
as follows:
Gas Flow
Corrected Volume (Rate & Total)
Mass (Rate & Total)
Temperature & Pressure
14 Operation

415-M-V3.2
Steam
Mass (Rate & Total)
Energy (Rate & Total)
Temperature & Pressure
Specific Weight & Enthalpy
If any value other than the default display values are selected, they will
remain displayed for 5 seconds, after which the display will automatically
revert to the default values.
Totals are displayed with a maximum of 8 digits, including decimals.
For example, if two decimals are programmed, the maximum total is
999,999.99, after which the totals roll over to zero and continue
counting.
For large flowrates, totals can be integrated at 1/1000 of the flowrate
by programming the Total Units function at x 1000. The units of
measure will then be displayed as follows:
SI Units
Rate Total
cm/h kcm
scm/h kscm
Nm3kNm3
kg/h tonne
MJ/h GJ
US Units
Rate Total
cft/h kcft
scft/h kscft
lbs/h klbs
BTU x 1000/h MBTU
(Note: k = x 1000, M = x 1,000,000, G = x 1,000,000,000).
The RESET key can be used to reset the totals whenever one of the totals
is displayed. Both totals will be reset at the same time. The RESET
switch can be disabled during calibration to prevent front panel resetting.
Operation 15

415-M-V3.2
3.2 FLOW EQUATIONS FOR GASES
This section applies only to gas flow measurement and, if the Model 415 is to
be used for steam measurement, the reader can skip this section and go to
section 3.3.
The Model 415 will accept inputs from a wide range of flowmeters with
the flowrate calculated by the equations defined below. Both mass flow
and volume corrected flow to a base temperature and pressure are
calculated and displayed in either SI (metric) or US units. For an
explanation of the symbols used in the equations see the list at the
beginning of this manual.
Two basic formulae are common to all equations:
1. Specific Gravity, G = Molecular Weight of Gas
Molecular Weight of Air
.....(1)
=Molecular Weight of Gas
28.9625
2. DensityofaGas,ᴘ,atbaseconditions:
In SI Units
kg/m3.....(2)rB= 3.4834 G PB
ZBTB
In US Units
lbs/ft3.....(3)rB= 2.6988 G PB
ZBTB
Standard Conditions
Standard conditions are defined as:
15°C (288.15°K) and 101.325 kPa
or 59°F (518.67°R) and 14.69595 psia.
16 Operation

415-M-V3.2
Normalised Conditions (SI Units only)
Normalised conditions are defined as:
0°C (273.15°K) and 101.325 kPa.
A. Volumetric Flowmeters With Frequency Output.
eg. Vortex, turbine or positive displacement flowmeters.
......(4)
QVB =N. frequency(Hz)
KF. PF
PB. TB TF. ZB ZF
......(5)QM=rB . QVB
B. Volumetric Flowmeters With 4-20mA Output.
eg. Vortex, turbine or positive displacement flowmeters with
frequency to current convertors.
TB
TF. ZB ZF
. .A
QM= rB.QVB
C. Differential Pressure Flowmeters With 4-20mA Output And A Square
Law Relationship.
eg. Orifice Plates, Averaging Pitot Tubes, Target Flowmeters, etc.
......(7)QVB = SVB . PF
PB. TB TF. ZB ZF. A
QM= rBQVB
Operation 17
QVB = SV .
TB
TF.

415-M-V3.2
D. Differential Pressure Flowmeters With 4-20mA Output And With A
Linear Flow Relationship.
eg. D.P. transmitters with a square root extractor or VA meters.
......(8)QVB = SVB . PF
PB. TB TF. ZB ZF
. A
QM
=rB.
QVB
Note that the pressure and temperature are still square rooted, even
though the flow signal A is not. This is because the output from the D.
P. transmitter is not truly volumetric, but will be affected by a change in
density of the gas being measured. Therefore, the equations
relating to differential pressure will apply.
E. Dual Differential Pressure Flowmeters With 4-20mA Output.
To increase the range over which flow can be measured, two D.
P. transmitters with different spans can be connected across a
common orifice or other differential pressure device.
Equations 5 & 6 or 7 & 8 above would be used depending upon
whether the D. P. transmitters have square root extractors. Separate
scaling using these equations is then programmed for each
transmitter.
At lower flowrates, transmitter 2 will be used as a basis of
measurement and at higher flowrates, transmitter 1 will be used.
The crossover point will occur when the input on transmitter 2
exceeds 20mA.
18 Operation