Fisher 244ER Sensor Lead Wire Resistance Effect RTD Input, Given, Total cable length = 150 m

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Sensor Lead Wire Resistance Effect

Rosemount Models 244EH and 244ER PC-Programmable Temperature Transmitters

Table 2-1. Examples of Approximate Basic Error

Sensor Lead Wire Resistance Effect

RTD Input

When using a 4-wire RTD, the effect of lead resistance is eliminated and has no impact on accuracy. However, a 3-wire sensor will not fully cancel lead resistance error because it cannot compensate for imbalances in resistance between the lead wires. Using the same type of wire on all three lead wires will make a 3-wire RTD installation as accurate as possible. A 2-wire sensor will produce the largest error because it directly adds the lead wire resistance to the sensor resistance. For 2- and 3-wire RTDs, an additional lead wire resistance error is induced with ambient temperature variations. The table and the examples shown below help quantify these errors.

Sensor Input

Approximate Basic Error

 

 

4-wire RTD

None (independent of lead wire resistance)

3-wire RTD

± 1.0 Ω in reading per ohm of unbalanced lead wire

 

resistance (Unbalanced lead wire resistance =

 

maximum imbalance between any two leads.)

2-wire RTD

1.0 Ω in reading per ohm of lead wire resistance

 

 

Examples of Approximate Lead Wire Resistance

Effect Calculations

Given:

Total cable length = 150 m

Imbalance of the lead wires at 20 °C = 0.5 Ω Resistance/length (18 AWG Cu) = 0.025 Ω/Ω °C Temperature coefficient of copper (αCu) = 0.0039 Ω/Ω °C Temperature coefficient of platinum (αPt) = 0.00385 Ω/Ω °C Change in Ambient Temperature (ΔTamb) = 25 °C

RTD Resistance at 0 °C (Ro) = 100 Ω (for Pt 100 RTD)

Pt100 4-wire RTD: No lead wire resistance effect.

Pt100 3-wire RTD:

Basic Error =

Imbalance------------------------------of-------Lead---------------Wires-------------

 

 

 

Pt × Ro)

 

 

 

Cu) × (ΔTamb) × (Imbalance of Lead Wires)

Error due to amb. temp. variation = ----------------------------------------

-----(---α----Pt-----)---×-----(--R-----o---)---------------------------------------------

 

 

 

Lead wire imbalance seen by the transmitter = 0.5 Ω

Basic error =

0.5 Ω

 

= 1.3 °C

(---0.00385------------------------Ω------/----Ω-------°---C-----)---×-----(---100------------Ω-----)

 

Error due to amb. temp. var. of ± 25 °C

 

 

= (---0.0039----------------------Ω-----/----Ω-------°---C-----)---×-----(--25---------°---C-----)---×-----(---0.5----------Ω-----)-

= ±0.13 °C

(0.00385 Ω / Ω °C) × (100 Ω)

 

 

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Contents 00809-0100-4737 English Rev. EA Models 244EH and 244ER PC-Programmable Temperature TransmittersPage Product Manual Models 244EH and 244ER PC-Programmable Temperature Transmitters¢00809-0100-4737f¤ 00809-0100-4737 Rev EA 10/00Page Table of Contents InstallationMaintenance and TroubleshootingAPPENDIX A Reference DataAPPENDIX B ApprovalsSAFETY MESSAGES Section1 Introduction MANUAL OVERVIEW CONSIDERATIONS GeneralMechanical ElectricalPage 2 Installation SAFETY MESSAGES WarningsTOOLS NEEDED FOR INSTALLATION The tools needed for installation are as followsFigure 2-1. Transmitter Installation Flowchart MOUNTING ExampleSpecial Mounting Considerations Mounting a Model 244EH to a DIN RailINSTALLATION PROCEDURES TransmitterHead Mount Transmitter with DIN Plate Style Sensor Figure 2-6. Typical Model 244EH Transmitter Mounting Configuration Using Threaded Style Sensorand Assembly Head Mount Transmitter with Threaded SensorFigure 2-7. Typical Rail Mount Transmitter Mounting Configuration Using Integral Mount Sensor and AssemblyTo complete the assembly, follow the procedure described below 6. Run sensor lead wires from the sensor assembly to the transmitterRail Mount Transmitter with Threaded Sensor 644-0000A04BConfiguration Software Multichannel InstallationsSystem Requirements Choose the procedure that matches the operating system you are using Procedure for Windows 3.1 or Windows for WorkgroupsProcedure for Windows 95 or Windows NT Model 244EC Configuration Interface Setting Up the Model 244EC Configuration InterfaceScreen Conventions FIELD WIRING Figure 2-10. Complete Transmitter Configuration SystemSensor Connections RTD or Ohm InputsSensor Lead Wire Resistance Effect RTD Input Examples of Approximate Lead Wire Resistance Effect CalculationsGiven Total cable length = 150 mThermocouple or Millivolt Inputs FAILURE MODE Changing Switch Positions Figure 2-13. Transmitter Power, Sensor, and Configuration TerminalsPOWER SUPPLY Surges/Transients 3 OperationCONFIGURATION GroundingConfiguring a Single Transmitter Figure 3-1. Models 244EH and 244ER Configuration Software MainConfiguration Window Configuring Several Transmitters Identically Viewing the Process Variable INTERMITTENT SENSOR ALGORITHMFigure 3-2. Viewing the Process Variable with the 244EC Case Examples Case 1 Open SensorCase 2 Temperature Change Greater than the Threshold Value2% of Output RangeIntermittent Sensor Algorithm and Damping Case 3 Temperature Change Within the Threshold Value 2 % of RangeIntermittent Sensor Detect Advanced Feature 2.0 seconds, the transmitter outputs the reading that corresponds tothe damping curve at that time , and continues to calculate and continues to approach the input curveaccordingto theequation aboveImplementation Transmitter Behavior with Intermittent Sensor Detect ONTransmitter Behavior with Intermittent Sensor Detect OFF Page 4 Maintenance and Troubleshooting SAFETY INFORMATIONTROUBLESHOOTING Model 244EH software version Troubleshooting Chart Error MessageCause and Possible Solutions TABLE 4-1. Models 244EH and 244ERTRANSMITTER SPECIFICATION Functional AppendixA Reference Data Power SupplyPerformance Update TimePower Supply Effect CE Electromagnetic Compatibility Compliance TestingAccuracy TABLE A-2. Model 244E Input Options and AccuracySensor InputTransmitters can be installed in locations where the ambient Ambient Temperature EffectPhysical WeightElectrical Connections Materials of ConstructionORDERING INFORMATION ModelProduct Description HeadTABLE A-5. Model 244EC Configuration Interface Ordering Information TABLE A-6. Transmitter AccessoriesTypical Model Number 244EC Part DescriptionStandard Configuration Custom ConfigurationUnless specified, transmitter will be shipped as follows TaggingDIMENSIONAL DRAWINGS Transmitter Enclosure and Model 244EC Configuration InterfaceConfiguration Interface Model 244ERPage HAZARDOUS LOCATIONS INSTALLATIONS B ApprovalsLOCATIONS CERTIFICATIONS Factory Mutual FM ApprovalsCanadian Standards Association CSA Approvals Standard Australia Quality Assurance Service SAA KEMA ApprovalsSpecial Conditions for Safe Use INSTALLATION DRAWINGS GostandartFigure B-1. Canadian Standards Association CSA Intrinsic Safety Installation Drawing Rev. ABInstallation Drawing Rev. AA Figure B-2. Canadian Standards Association CSA Explosion-ProofFigure B-3. Factory Mutual FM Intrinsic Safety Installation Drawing 00644-0009, Rev. AAFigure B-4. Factory Mutual FM Explosion-Proof Installation Drawing 00644-1049, Rev. ABC Models 644 and 244E Temperature Transmitters Manual Supplement Transmitter Design Sensor Wiring Diagrams Special Mounting OLD TRANSMITTERConsiderations Models 644H and 244EHNEW TRANSMITTER Considerations HART Communicator Model 644H only2. Select 1 Off-line, 1 New Configuration, Rosemount, 644 Temp Use with an Existing DIN Plate Style SensorSPECIFICATIONS BASEFFA1 Intrinsically Safe Installation Entity ParametersFactory Mutual3 Entity ParametersIndex Wiring Page Product documentation available at