Temperature Calibration APPLICATIONS AND SOLUTIONS
INTRODUCTION Temperature devices in process manufacturing environments provide measurements to the process plants’ control systems. The performance of these temperature instruments is often critical to optimized operation of the process manufacturing plant or proper functioning of the plant’s safety systems. Process temperature instruments are often installed in harsh operating environments, causing their performance and the performance of their sensors to shift or change over time.
TABLE OF CONTENTS APPLICATIONS Automating Transmitter and Sensor Calibrations.............................. 4 Automating Temperature Calibration at the Bench........................... 6 HART Smart Temperature Transmitter Calibration............................. 8 Calibrating and Testing RTD Sensors.............................................. 10 Calibrating and Testing Thermocouple Sensors ........................... 12 Simulating Thermocouples and RTDs for Calibration and Testing.......................
Automating Transmitter and Sensor Calibrations Temperature transmitter calibrations are often performed without taking into account temperature sensor performance. For many processes this has been an acceptable practice, although the sensor typically contributes more errors than the transmitter. This practice can be problematic for critical process measurements or those that need a higher degree of confidence or accuracy.
Hart Dry-well cable kit, P/N 2111088 754 DOCUMENTING PROCESS CALIBRATOR Interface cable Null modem Fluke Calibration Dry-well (DB9) Fluke Calibration 3.5 mm interface cable Fluke Calibration Dry-well (3.5 mm) To perform the test: To use a dry-well calibrator with a Fluke 754 to automatically test a transmitter with sensor: STEP Remove the process measure- 1 ment sensor and install into the dry-well temperature calibrator.
Automating Temperature Calibration at the Bench Automating temperature calibration has many advantages. For example, technicians need automation because they are under tremendous pressure to do more with limited resources, and automation can help reduce the number of repetitive time-consuming tasks required to complete a calibration.
Temperature Source Control Output TECH TIPS Unit Under Test Reference Probe 100.00°C F1 F2 F3 • Only one temperature source can be connected at a time. F4 Example Temperature Control Source To perform the test: STEP Connect the calibrator to the temperature source with the appropriate 1 data cable. • The 1586A allows you to set the required stability band to accept a temperature measurement. • The 1586A comes with Fluke DAQ 6.0 software, which allows you to handle and visualize your data.
HART Smart Temperature Transmitter Calibration Smart temperature transmitters, with their flexibility and enhanced accuracies, have become the number one temperature calibration workload for instrumentation professionals. Calibrating a HART smart temperature transmitter requires an accurate temperature simulator or temperature source, mA measurement, and a HART communication tool for calibration. You can use separate tools or a calibrator that integrates all three to perform this task.
Simulating Thermocouples and RTDs for calibration and testing TEST DC PWR – ++ – TEST DC PWR – ++ – TECH TIPS TC transmitter calibration connection TC transmitter calibration connection 754 DOCUMENT 754 DOCUMENT ING PROC ESS CALIB RATOR C-1 C-2 ING PROC ESS CALIB RATOR C-1 C-2 S-2 TEST DC PWR – ++ – S-4 S-2 TEST DC PWR – ++ – S-1 S-4 S-1 S-3 RTD transmitter calibration S-3 connection RTD transmitter calibration connection To perform the test: ©2015 Fluke Corporation.
Calibrating and Testing RTD Sensors Typically RTDs are checked while calibrating the connected device, such as a panel meter or temperature transmitter. However, if a problem is suspected with a temperature sensor, sensor calibrations can be performed separately from the calibration of process electronics. Field checks of temperature sensors can be easily performed with a dry-block or Micro-Bath. For best results, a full calibration of a temperature sensor is performed at the bench.
100.2° C MENU ENTER 100.00°C F1 F2 F3 F4 100.00°C F1 F2 F3 F4 To perform the test: STEP Isolate the sensor from the process. 1 STEP Fully immerse the sensor into a precision temperature source, such as a 2 dry-well or bath capable of covering the required temperature range. TECH TIPS • Dry-wells have inserts that are interchangeable and have a variety of hole patterns to accommodate various probe sizes.
Calibrating and Testing Thermocouple Sensors Thermocouples are common in industry because they are inexpensive and cover a wide temperature range. They should be tested during commissioning and again when removed from a process to verify that tolerances were met. Additionally, thermocouples may be tested at regular calibration intervals and when suspected of failing to meet their performance specifications.
100.00°C 266.03°C SETPT: 266.00 °C HEAT: 22 •/• TC—T : 265.783 °C F1 F2 F3 F4 F1 F2 F3 F4 To perform the test: STEP Isolate the sensor from the process. 1 STEP Fully immerse the sensor into a precision temperature source such as a 2 dry-well or bath capable of covering the required temperature range. STEP To check the calibration of the thermocouple separately from control 3 TECH TIPS system temperature indicator, disconnect the thermocouple from the electronics.
Simulating Thermocouples and RTDs for Calibration and Testing Thermocouples and RTDs are the most common sensors used in process temperature measurements. Simulating a process sensor signal into a process instrument or control system input enables a technician to verify whether the device responds correctly to the temperature measured by the instrument. There are many different ways to simulate these sensors for testing purposes.
Simulating Thermocouples and RTDs for calibration and testing TEST DC PWR – ++ – TEST DC PWR – ++ – TC transmitter calibration connection TC transmitter calibration connection 754 DOCUMENT 754 DOCUMENT ING PROC ESS CALIB RATOR C-1 C-2 ING PROC ESS CALIB RATOR C-1 C-2 S-2 TEST DC PWR – ++ – S-4 S-2 TEST DC PWR – ++ – S-1 S-4 S-1 S-3 RTD transmitter calibration S-3 connection RTD transmitter calibration connection To perform the test: ©2015 Fluke Corporation.
Using a Precision Thermometer for Single Point Process Temperature Verification It’s not always possible or practical to remove instruments from a process for calibration. In situ verification at a single point may be the only way to know whether an instrument is performing as expected. A single point verification is most effective over a narrow temperature range and when combined with other trends and information related to the process and equipment.
RS 232 T1 30 V MAX 12 V DC T2 1524 CALIBRATION THERMOMETER READOUT RESET STATS mV TREND °C °F HOLD SETUP LOG HOME SAVE ENTER RECALL To perform the test: STEP The test well (thermowell) should be within a few inches of the 1 temperature transmitter and sensor assembly to be tested. STEP Make sure that the probe of the temperature standard is long 2 enough to reach the bottom of the test well and that air gaps between the probe and well are minimized.
Temperature Switch and Controller Testing in the Field Temperature switches and controllers are commonly used in small processes and in control loops where a programmable logic controller (PLC) or larger distributed control system (DCS) are not warranted. Temperature controllers provide both switching capability based on rising and dropping temperatures, as well as a local indication of the measured temperature.
754 DOCUMENTIN G PROCES S CALIBRA TOR TECH TIPS 200.0° C MENU ENTER To perform the test: To use a thermocouple simulator to test a switch with a thermocouple input: STEP Disconnect the process measurement sensor. 1 STEP Connect the mini-connector from the test wires to the TC source 2 connection of the calibrator (figure above). STEP Connect the calibrator resistance measurement terminals to the 3 switch contacts to measure continuity.
Temperature Switch and Controller Testing at the Bench A temperature switch is a device that protects a thermal system by sensing temperature and closing or opening a switch to shut down a process or equipment if the temperature is outside the safe range. Temperature switches are often calibrated or tested for safety reasons to determine how accurate and repeatable the device is.
Temperature Switch sets - closed Deadband Set-point Reset Switch resets - open TECH TIPS • Set the scan rate to a low value, i.e. 1.0 °C per minute, for better accuracy. • If the scan rate is too low, the duration of the test may be longer than necessary. Time To perform the test: STEP Isolate the switch from the process. 1 STEP Fully immerse the switch into a precision temperature source such as a 2 dry-well or bath capable of covering the required temperature range.
Calibrating with a Micro-Bath Instrument technicians need to calibrate a wide variety of temperature sensors including liquidin-glass thermometers, dial gauges, and sensors that come in odd shapes and sizes. Problems of fit and immersion that may occur with short, square, or odd-shaped sensors are practically eliminated in a Micro-Bath because the probes are immersed in a fluid that is magnetically stirred for optimal stability.
TECH TIPS 125.0° C MENU 7103 MICRO-BATH –30°C to ENTER • Caution: the fluid level rises with higher temperatures and with the number and size of the probes placed into the fluid. 125°C -25.0 C SET DOWN UP EXIT 7103 MICRO-BATH –30°C to 125°C 125.0 C SET DOWN UP EXIT • Best results are obtained with the probe inserted to the full depth of the well. • The stabilization time of the Micro-Bath depends on the conditions and temperatures involved.
Infrared Thermometer Test and Calibration Infrared thermometer calibrations can be accurate with the proper setup and planning. It’s important to choose a calibrator with a radiometrically calibrated target that is large enough to accommodate the recommended calibration distance of common infrared thermometers, along with their various fields of view.
Measuring (d) distance d Manufacturer recommended large target TECH TIPS IR thermometer spot size 561 HVACPro IR THERMOMETER • Emissivity makes a big difference in infrared temperature measurement. 199.3 Smaller target = IR thermometer field of view To perform the test: STEP Allow at least 15 minutes for the IR thermometer to reach the 1 temperature of the shop or laboratory. STEP Set the radiation source to the desired calibration temperature.
Loop Calibration with a Temperature Transmitter at the Bench In industrial process industries, temperature measurement equipment usually has two components: a sensing device such as an RTD or thermocouple and a transmitter to read and relay the signal to the control system. All sensors, including RTDs, drift with time. Thus, testing the transmitter and not the sensor could result in misjudgment regarding a system’s performance.
TEST DC PWR – ++ – TECH TIPS 100.00°C F1 F2 F3 F4 • Streamline the process with automation and provide documentation using a Fluke 754. • Seventy-five percent of the errors in a temperature measurement system comes from the sensor. • At minimum, you need a calibrator, and a device to measure 4-20 mA and power the loop. To perform the test: • Choose a temperature standard with a 90 degree angle bend to ensure both the temperature standard and the transmitter fit in the dry-well at the same time.
TEST TOOLS Pick the right temperature tool for you TEMPERATURE TOOLS SELECTION GUIDE Models 712B/ 714B 724/ 725/ 726 753/ 754 9142/9143/ 9144/9190A 9100S/ 9102S • • 9009 6102/ 7102/ 7103 4180/ 4181 1551/ 1552 1523/ 1524/ 1586A • • • • • 1620A 7526A Applications Temperature sensor calibration Temperature transmitter calibration Temperature Switch testing • • • 725Ex/726 • • • • • • • Source Temperature simulation RTD or TC (Source) 712B RTD, 714B TC • • Infrared temperature
Fluke 754 Documenting Process Calibrator-HART Fluke 724 Temperature Calibrator The Fluke 724 Temperature The Fluke 754 Documenting Calibrator can measure and source Process Calibrator-HART does the thermocouples and RTDs, plus volts work of several tools - sourcing, and ohms. Now you can carry one simulating and measuring prestool to expertly test all the temsure, temperature, and electrical perature sensors and transmitters signals in one rugged, handheld in your plant. device.
continued from page 29 Summary specifications • Measure and source mA and voltage to 0.02% • Source and measure RTDs to +/- 0.2 °C • Source and measure Thermocouples to 0.
Fluke 1551A, 1552A Stik Thermometer The Fluke 1551A and 1552A Stik Thermometers are an accurate and repeatable substitute to mercuryin-glass thermometers. Whether working outdoors in environments where potentially explosive gases may be present or on the floor of a processing plant, these intrinsically-safe, battery operated, portable reference thermometer are designed to go where you work.
6102, 7102, 7103 Micro-Baths Micro-Baths provide a convenient way to eliminate the problems of fit and immersion when calibrating short, square, or odd-shaped sensors. Proprietary controllers make the Fluke 6102, Fluke 7102, and Fluke 7103 Micro-Baths extremely stable. They are lighter and smaller than most dry-wells, have a spill-proof lid, and a convenient carrying handle, so you can easily take them where you need to go without a cart and without removing the fluid.
9100S, 9102S Handheld Dry-Well Calibrators 9150 Thermocouple Furnace below ambient. Summary specifications Stability: ±0.5 °C Temperature range: 150 °C to 1200 °C Controller accuracy: ±5 °C across its entire range The 9150 is a low cost portable thermocouple The Fluke Calibration 9100S furnace. It has a removable well insert for versatility and rapid cool-down and heat-up times.
9142, 9143, 9144 Field Metrology Wells 9190A Ultra-Cool Field Metrology Well Whether you need to calibrate 4-20 mA transmitters or a simple thermostatic switch, a Field Metrology Well is the right tool for the job. With three models covering the range of –25 °C to 660 °C, this family of Metrology Wells calibrates a wide range of sensor types.
INTRINSICALLY SAFE TEMPERATURE TOOLS The Fluke 1551A and 1552A “Stick” Thermometer Readouts are an intrinsically safe digital substitute for your mercury-inglass thermometers. Accurate and repeatable to ± 0.05 °C over their full range, the 1551A and 1552A are the “gold standard” of industrial temperature calibration.
ACCESSORIES Precision PRTs Fluke Calibration offers these and other precision thermometer probes to meet the needs of a wide variety of industrial calibration applications. When ordering a PRT, indicate the length of the probe and the type of readout it will connect to by adding the following extensions to the model number: For length use (-6 for 6 in, -9 for 9 in or -12 for 12 in). To indicate the model of the readout use (-P for 1523/1524, -L for 1586A, –A for 914X, and –D for 917X).
Fluke 700TC2 Thermocouple Mini-Plug Kit Type J, K, T, E, R/S Surface measurements For use with: Fluke 700, 720 or 740 Series Process Calibrators, Fluke 714 Thermocouple Thermometer. Type K thermocouple with exposed junction for flat or slightly convex surfaces such as plates and rollers. • 1.3 m (4 ft) lead • 9.525 cm (3.
Pipe measurements 80PK-8 and 80PK-10 Pipe Clamp Temperature Probe Type K thermocouple clamps securely to pipes for fast temperature and superheat measurements. • Durable ribbon sensor • 1 m (39 in) lead • 80PK-8 for pipe diameters 6.4 mm to 34.9 mm (0.25 in to 1.375 in) • 80PK-10 for pipe diameters 32 mm to 64 mm (1.25 in to 2.5 in) • Measurements are repeatable to 0.
SOFTWARE MET/TEMP II LogWare III MET/TEMP II is automated temperature calibration software that allows you to eliminate long manual temperature calibration processes. Test thermocouples (all types), RTDs, SPRTs, thermistors, and even liquid-in-glass thermometers (LIGs). Virtually any sensor with a resistance or voltage output can be tested, up to 100 sensors at a time.
Software, continued from page 39 TQAero Thermal Validation Software for AMS 2750 Compliance TQAero software provides qualification, reporting, documentation and audit trail management to support compliance with National Aerospace and Defense Contractors Accreditation Program (NADCAP) and SAE International AMS 2750 guidelines covering heat treating applications in aerospace and transportation industries.
