RTD SENSOR FisherRosemount Korea TEMPERATURE 1 FRKLMAY 2000

RTD SENSOR Fisher-Rosemount Korea TEMPERATURE 1 FRKL/MAY 2000

Typical Assembly of Transmitter and Sensor TEMPERATURE 2 Headmount Transmitter Extension length Cable Entry Head connection Instrument Connection Thread Thermowell Immersion length (U-length) Stem Fisher-Rosemount Korea Mounting arrangement FRKL/MAY 2000

RTD Sensors TEMPERATURE 3 What is an RTD ? Resistance Temperature Detector – Operation depends on inherent characteristic of metal (Platinum usually): electrical resistance to current flow changes when a metal undergoes a change in temperature. – If we can measure the resistance in the metal, we know the temperature! – Platinum resistance changes with temperature Wire-wound sensing element Rosemount’s Series 78, 88 Fisher-Rosemount Korea Thin-film sensing element on ceramic substrate Rosemount’s Series 65 68, 58 Two common types of RTD elements: FRKL/MAY 2000

RTD Sensors TEMPERATURE 4 What is a RTD Element ? Class A RTD Wire Wound Class B RTD Thin Film M. I. Cable (Mineral Insulated Cable), SST or Inconel depending on temperature Fisher-Rosemount Korea FRKL/MAY 2000

Rosemount RTD Construction TEMPERATURE 5 Sensor Differentiation Explosion Proof Approvals Calibration Services RTD Technology: Proprietary method of packing, O-ring Molded rear house assembly Al 2 O 3 packing for O-ring for protection against vibration against moisture Fisher-Rosemount Korea FRKL/MAY 2000

Rosemount RTD Differentiation TEMPERATURE 6 Sensor Response Time Improved u Type of element Platinum Rosemount has externally wound RTD for faster response time – Thin-film has slightly faster response time than wirewound – – u Element packaging Rosemount RTD’s are packed in aluminum oxide to provide optimum thermal conduction within the sheath – Grounded thermocouples are twice as fast as ungrounded – u Sheath thickness and material – Rosemount uses 316 SST and Inconel (for high temperatures) for sheath; both are very good thermal conductors Fisher-Rosemount Korea FRKL/MAY 2000

RTD Sensors Interchangeability TEMPERATURE 7 Class B Class A = 0. 15 + 0. 002 |t| Class B = 0. 3 + 0. 005 |t| Fisher-Rosemount Korea FRKL/MAY 2000

RTD Sensor TEMPERATURE 8 Why is Platinum used ? It is the most stable & near linear resistance versus temperature function when compared to other metals like thermistor, Nickel & Balco Fisher-Rosemount Korea FRKL/MAY 2000

Question TEMPERATURE 9 What does it mean Pt 100, = 0. 0385? Pt = Platinum 0. 0385 = 0 deg. C the probe will read 100 ohms. at 100 deg. C, it will read 138. 5 ohms. Fisher-Rosemount Korea FRKL/MAY 2000

RTD Sensors : Wiring TEMPERATURE 10 4 - wire to 3 or 2 wire For 3 -wire systems use one white and two red leads. Do not common White leads. Insulate or terminate the unused wire in a manner that avoids short circuiting to ground or earth For 2 -wire systems common both sets of leads Fisher-Rosemount Korea FRKL/MAY 2000

Vol I - RTD Series TEMPERATURE 11 Temperature vs relationships and Tolerances confirm to IEC 751. RED WHITE All Single Element Sensors are supplied as 4 Wire WHITE RED GREEN BLACK All Duplex Element Sensors are supplied as 2 x 3 Wire r Fisher-Rosemount Korea 0. 25 inches sheath diameter FRKL/MAY 2000

Vol II - Series 65 RTD TEMPERATURE 12 Temperature vs relationships and Tolerances confirm to IEC 751. RED WHITE Note: Wire colors different from Vol. 1 RED All Single Element Sensors are supplied as 4 Wire BLACK BLUE GREEN All Duplex Element Sensors are supplied as 2 x 3 Wire r r Range: -50 to 450°C Standard 6 mm sheath diameter 321 SST sheath material Class B Tolerance Fisher-Rosemount Korea FRKL/MAY 2000

RTD Sensors TEMPERATURE 13 2, 3, & 4 -Wire RTDs Why use a 2 -, 3 -, or 4 - wire RTD? – 2 -wire: Lowest cost -- rarely used due to high error from lead wire resistance – 3 -wire: Good balance of cost and performance. Good lead wire compensation. – 4 -wire: Theoretically the best lead wire compensation method (fully compensates); the most accurate solution. Highest cost. 4 -wire RTD Red Sensing Element (I. e. wire-wound, thin film) White Fisher-Rosemount Korea Black Red Typically use copper wires for extension from the sensor Green Blue FRKL/MAY 2000

Temperature Sensor : Stability, Repeatability & Linearity TEMPERATURE 14 Resistance (W) How does these factors affect Your Measurement ? F Inconsistent Quality F Introduce downstream variation F Waste raw material - rework or disposal ! F Lost Production F High energy cost F Lost profits 1 C IE 75 r Cu ve Temperature (o. C) Fisher-Rosemount Korea FRKL/MAY 2000

Temperature Sensor : Stability F TEMPERATURE 15 Stability is expressed as drift in the temperature reading per unit time, as a drift in resistance per unit time expressed in ohms or as a percentage of resistance. Stability specifications are often define in terms of a temperature exposure history. IEC 751 defines Stability as the limit of drift after 250 hours of exposure to full scale temperature. < 0. 005 Deg C/year for laboratory grade <0. 1 Deg C of FS/year for thin film Platinum RTD for normal usage F <0. 05 Deg C per 5 -years for temperature ranges -40 to 125 Deg C Fisher-Rosemount Korea FRKL/MAY 2000

Temperature Sensor : Repeatability TEMPERATURE 16 Repeatability is the range of output that the PT RTD will give when arriving at a target temperature in repetitive cycles from the same direction. F F Bi-directional repeatability is the output range when a target temperature is approached from two directions. F Hysterisis is the difference in the mean values of the two direction dependent output ranges when arriving at a target temperature in repetitive cycles from both directions. IEC 751 defines Repeatability to be the drift observed at 0 Deg C after a sensor experience 10 cycles over its full operating temperature range. F Fisher-Rosemount Korea FRKL/MAY 2000

RTD Sensors TEMPERATURE 17 Resistance changes are repeatable How does a RTD works? Resistance Temperature Detector – The resistance changes of the platinum wiring can be approximated by an ideal curve -- the IEC 751 International Resistance vs. Temperature Chart: o. C 0 10 20 30 Ohms 100. 00 103. 90 107. 79 111. 67 IEC 751 Page 3 -2: Sensors PDS (V. 1) Fisher-Rosemount Korea Resistance (Ohms) – IEC 751 Temperature (o. C) FRKL/MAY 2000

Temperature Sensor : Linearity TEMPERATURE 18 Linearity is defined as the deviation of the output-versustemperature curve, from the best fit linear approximation of the devices behaviour over the operating temperature range. F It is expressed as either a percentage of full scale output or as the maximum deviation (either in Ohms or Deg C for an RTD) Resistance (W) F e C IE 1 75 rv Cu Temperature (o. C) Fisher-Rosemount Korea FRKL/MAY 2000

RTD Sensor Joining Techniques Recommended Temperature Range Soldering - 30 to 120 Deg C Crimping - 50 to 200 Deg C Brazing - 50 to 400 Deg C Spot welding Laser welding - 50 to 600 Deg C - 50 to 850 Deg C Fisher-Rosemount Korea TEMPERATURE 19 Comments remove flux to prevent corrosion more than 180 Deg C high melting soldering material is used max. allowable tensile strength of the wires used are not exceeded Do not ‘burn’ the RTD chip during blazing process. Remove flux to prevent corrosion. Both spot & laser welding are most secure & temperature resistant. A high level of skill & manufacturing know how with strict adherence to manufacturing parameters. FRKL/MAY 2000

Temperature : International Standards Fisher-Rosemount Korea TEMPERATURE 20 FRKL/MAY 2000

What other consideration? TEMPERATURE 21 · The useful range of thermocouple type. · The sheath material maximum operating temperature. · The de-rate upper temperature limit due to sensor diameter. The same element with different sheath diameter will affect temperature limit as well. Example : Thermocouple Type K Sheath diameter : 5 mm Sheath material : Inconel Measuring range : 0 to 1100 deg. C For this combination, the sensor will fail although maximum measuring range is 1372 deg. C. · The temperature rating of other components such as connectors, transition joints and wire. Fisher-Rosemount Korea FRKL/MAY 2000

Sensor Lead-Wire Length : RTD F F F TEMPERATURE 22 Sensor Direct Wiring : Recommended Maximum 250 feet using 18 AWG lead wire For 3 -wire RTD, maximum error 0. 16 Deg F per 100 feet using 18 AWG lead wire. For best RTD wiring practice to reduce error : use same specification & run-length lead-wires 0 Fisher-Rosemount Korea FRKL/MAY 2000

Temperature Point Response Time TEMPERATURE Factors Affecting Temperature Point Response Time Thermowell Sensor 4 Thermowell 4 Transmitter 4 Process 4 75. 4 °C Sensor Process Transmitter Fisher-Rosemount Korea FRKL/MAY 2000

Sensor Time Response TEMPERATURE Factors Affecting Sensor Response Time OD Type of element Wirewound RTD » externally or internally wound – Thin-film RTD – Thermocouple – Element packaging Element coating, potting – Contact between element package & sheath – sheath ceramic bore element Al 2 O 3 packing Sheath thickness and material Fisher-Rosemount Korea FRKL/MAY 2000

Sensor Time Response Industry Average TEMPERATURE Rosemount (Series 78) wirewound RTD 6. 0 - 7. 0 s 4. 7 s (Series 65 & 68) thin-film RTD 5. 0 - 5. 5 s 3. 38 s Ungrounded thermocouples <2 s Grounded thermocouples <1 s * All results based on standard conditions: time required to reach 63. 2% sensor response for water flowing at 3 ft/sec. RTD response times shown are the average + 6 sigma. Fisher-Rosemount Korea FRKL/MAY 2000

Factors Affecting Response Time of Sensors in Thermowells TEMPERATURE Thermowell design style (thickness at tip) – Stepped is the fastest Contact between sensor sheath and thermowell (x and y) Spring loaded sensor ensures contact at the tip (x=0) – Industry practice suggests using thermally conductive fill can significantly reduce time lag – x y Thermowell Sensor Assembly Thermally Conductive Fill Fisher-Rosemount Korea FRKL/MAY 2000

Time Response for Sensors in Thermowells TEMPERATURE Tapered thermowell 26 seconds Stepped thermowell 22 seconds Industry data shows stepped t-well with fill = 11 seconds * Based on externally published data for time required to reach 63. 2% sensor response for water flowing at 3 ft/sec. , with a sensor response time of 5. 5 seconds. Time response of assembled point is not additive. Fisher-Rosemount Korea FRKL/MAY 2000

Factors Affecting Transmitter Response Time TEMPERATURE Time response depends on element (complexity of calculation) 2 -wire RTD 440 - 760 ms l 3 & 4 -wire RTD 520 - 920 ms l Thermocouples 300 - 750 ms l Above is good provided the analog output changes less than 2% l Transmitter update time (output) every 500 msec Transmitter 75. 4 °C Process Fisher-Rosemount Korea FRKL/MAY 2000

Process Factors in Temperature Response Time Velocity of the material u Thermal conductivity of the material u Density and viscosity of the material Process time constants can be from seconds to hours: TEMPERATURE u 75. 4 °C Water @ 3 fps t = 3. 38 s Air at 50 fps, 40 -80 o. C = 38. 0 s Oil agitated in a bath: t = 43. 0 s Oil not agitated: t = >3 minutes Process Fisher-Rosemount Korea FRKL/MAY 2000

Response Time TEMPERATURE Sensor < 1 to 4. 7 sec Sensor in Thermowell 22 to 26 sec Transmitter . 5 to. 9 sec Process Seconds to Hours • Thermowells and process material/conditions have the greatest effect on temperature point response time • We are working on a method to predict time response of a temperature point through modeling of the time response in two known media Fisher-Rosemount Korea FRKL/MAY 2000

Frequently Asked Questions TEMPERATURE 31 Why should I buy an RTD when TC are more rugged & less expensive ? RTDs are more accurate, drift less over time & resistance to noise. Lower cost copper lead-wires compare the expensive TC-wires. What is RTD & PRT ? RTD is resistance temperature detector. It may use platinum, nickel or copper for its element. A PRT is a platinum resistance thermometer, an RTD that uses platinum for its element. What is the maximum distance between a PRT & a recorder or controller without using a transmitter ? We recommend 250 feet using at least 18 AWG lead wire without a transmitter. Further details can be check with recorder or controller supplier. Fisher-Rosemount Korea FRKL/MAY 2000

Frequency Asked Questions TEMPERATURE 32 How far can I run the signal with a temperature transmitter ? The only limitation is the transmitter’s minimum voltage (12 VDC) requirement at the terminals. A power supply must overcome the lead wire resistance. A long lead wire can act as an atenna, picking up stray electrical signal & causing RFI & EMI. Twisted shielded wire should be used for long runs or if the wires run next to other wires or electric motors. What is the minimum immersion length for an RTD ? Rule of thumb : At least 10 -times greater than the diameter of the sensor or thermowell plus the sensitive length of the PRT. This is to minimise stem conduction errors caused by heat conduction along the sheath or leadwires of a probe or along the length of a thermowell. The heat conduction increases or decreases the measured temperature depending on the applications & environmental conditions. Fisher-Rosemount Korea FRKL/MAY 2000

Frequently Asked Questions TEMPERATURE 33 How is the calibration of a PRT confirmed ? Simply measure the sensor’s ice point resistance (0 Deg C or 32 Deg F) and compare the measured value to its calibrated or previous value. If the ice-point resistance increase, it is a sign that the probe is being stressed (vibration or shocked) or that the probe is used beyond its rated temperature. A decrease in ice point resistance usually signals a problem with the moisture seal on the element. What is the difference between a. 00385 & a. 003902 probe ? The only difference is the amount that the resistance changes per degree of temperature. Both probes will read 100 ohm at 0 Deg C, but at 100 Deg C the. 00385 probe will read 138. 5 ohm and the. 003902 probe will read 139. 02 ohm. The sensor must be properly matched to the easuring device to obtain an accurate reading Fisher-Rosemount Korea FRKL/MAY 2000

Frequently Asked Questions TEMPERATURE 34 How can I determine if I have a. 00385 or. 003902 temperature coefficient ? The colour coding on the wires. White, Red -. 00385 Red, White -. 003902 Fisher-Rosemount Korea FRKL/MAY 2000