+---
+title: Temperature Measurement
+category: Instrumentation & Controls / Field Instrumentation
+toc_depth: 3
+description: >
+ When to use: selection, specification, procurement, installation, and commissioning of
+ field-mounted temperature sensing and transmitting assemblies for process control and
+ HVAC/mechanical systems — RTDs (Pt100/Pt1000), thermocouples (Types J, K, E, N, T),
+ bimetallic dial and filled-system thermometers, integral- and remote-mount temperature
+ transmitters, thermowells (flanged, threaded, socket-weld), connection heads, and
+ extension/compensating cable. Covers water/wastewater, industrial process, power,
+ pharma, food and beverage, commercial HVAC, and building automation, from cryogenic
+ (-200°C) through high-temperature process service (up to ~1260°C), with 4-20 mA,
+ HART, WirelessHART, FOUNDATION Fieldbus, and Modbus RTU outputs.
+ Not intended for: pressure/DP instruments ([[sync/pressure-instrumentation]]); flow
+ devices even when temperature-compensated ([[sync/flow-measurement]]); level sensors
+ ([[sync/level-sensors]]); loop architecture, P&ID conventions, and the instrument index
+ ([[sync/process-instrumentation]]); sensors integrated within packaged HVAC equipment
+ ([[sync/variable-air-volume-terminals]], [[sync/makeup-air-units]]); geotechnical
+ temperature arrays ([[sync/geotechnical-instrumentation-and-monitoring]]); heat-trace
+ control sensors wired to the heat-trace system; and laboratory-grade precision
+ thermometry or NIST-traceable calibration facilities.
+---
+
+# Scope {toc}
+
+## This standard governs field-mounted temperature sensing and transmitting assemblies used to measure, indicate, and transmit process and ambient temperature in process control and HVAC/mechanical systems.
+
+## The standard covers resistance temperature detectors, thermocouples, bimetallic and filled-system thermometers, integral- and remote-mount transmitters, thermowell assemblies, connection heads, and associated extension and compensating cable. {note}
+
+## It applies to temperature elements in pipe, vessel, duct, and ambient air service from cryogenic (-200°C) through high-temperature process service (approximately 1260°C thermocouple range), with 4-20 mA analog, HART, WirelessHART, FOUNDATION Fieldbus, and Modbus RTU output configurations. {note}
+
+## The standard addresses both process/industrial use cases (IEC/ISA-centric, thermowell-focused) and HVAC/building-automation use cases (duct sensors, room sensors, pipe-immersion sensors), because both fall within the Instrumentation and Controls discipline. {note}
+
+## The following are outside the scope of this standard and are governed elsewhere. {note}
+- Pressure and differential-pressure transmitters and gauges — see [[sync/pressure-instrumentation]].
+- Flow measurement devices (orifice plates, vortex meters, magnetic flowmeters), even when temperature-compensated — see [[sync/flow-measurement]].
+- Level sensors and level transmitters — see [[sync/level-sensors]].
+- Loop architecture, P&ID conventions, and the instrument index — see [[sync/process-instrumentation]].
+- Temperature sensors integrated within and shipped as part of packaged HVAC equipment (VAV box controllers, AHU discharge sensors) — see the relevant equipment standard such as [[sync/variable-air-volume-terminals]] or [[sync/makeup-air-units]].
+- Geotechnical temperature monitoring (ground temperature arrays, thermal conductivity testing) — see [[sync/geotechnical-instrumentation-and-monitoring]].
+- Electrical heat-tracing temperature sensors wired as part of the heat-trace control system.
+- Laboratory-grade precision thermometry and NIST-traceable calibration facilities.
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## ISA-MC96.1 has been withdrawn as a standalone standard and its technical content folded into ASTM E230 and IEC 60584; this standard references ASTM E230 as the primary US thermocouple authority and retains ISA-MC96.1 only for extension-wire color coding. {note}
+
+| Standard | Title |
+|----------|-------|
+| IEC 60751:2022 | Industrial Platinum Resistance Thermometers and Platinum Temperature Sensors |
+| ASTM E230/E230M-17 | Specification and Temperature-EMF Tables for Standardized Thermocouples |
+| IEC 60584-1:2013 | Thermocouples — Part 1: EMF Specifications and Tolerances |
+| ASME PTC 19.3 TW-2016 | Thermowells — Performance Test Codes |
+| ASME B40.200-2008 (R2013) | Thermometers, Direct Reading and Remote Reading |
+| ISA-MC96.1-1982 (R2018) | Temperature Measurement Thermocouples |
+| ISA-51.1-1979 (R1993) | Process Instrumentation Terminology |
+| NFPA 70 (NEC) | National Electrical Code (Article 250 Grounding, Article 500 Hazardous Locations) |
+| ANSI/ISA-12.27.01-2003 (R2019) | Requirements for Process Sealing Between Electrical Systems and Flammable or Combustible Process Fluids |
+| IEC 61511 / ISA-84.00.01-2004 | Functional Safety — Safety Instrumented Systems for the Process Industry Sector |
+
+# Submittals {toc}
+
+## The Contractor shall submit the following action submittals for each temperature instrument or assembly type prior to fabrication or procurement:
+- Product data sheets identifying sensor technology, range, accuracy class, output, and enclosure rating.
+- Completed instrument data sheets (ISA-20 format or Engineer-approved equivalent) for every tag.
+- Thermowell dimensional drawings with insertion length, bore, root and tip diameters, and process connection.
+- ASME PTC 19.3 TW-2016 wake-frequency calculations for every thermowell in flowing process service.
+- Hazardous-area certification (intrinsic safety, explosion-proof, or non-incendive) for instruments in classified areas.
+- Material certifications and, where wetted, mill test reports for thermowell stock.
+
+```datasheet
+label: Action Submittals
+type: checkbox
+options:
+ - Product data sheets
+ - Instrument data sheets (ISA-20)
+ - Thermowell dimensional drawings
+ - ASME PTC 19.3 TW wake-frequency calculations
+ - Hazardous-area certification
+ - Material certifications / mill test reports
+default:
+ - Product data sheets
+ - Instrument data sheets (ISA-20)
+ - Thermowell dimensional drawings
+ - ASME PTC 19.3 TW wake-frequency calculations
+```
+
+## The Contractor shall submit the following informational submittals:
+- Factory calibration certificates, NIST-traceable where required by this standard.
+- Manufacturer installation, operation, and maintenance instructions.
+- Loop diagrams showing element, transmitter, cable type, and DCS/PLC termination.
+- For safety-instrumented applications, the IEC 61511 SIL capability statement and proof-test procedure.
+
+```datasheet
+label: Informational Submittals
+type: checkbox
+options:
+ - Factory calibration certificates
+ - Installation/operation/maintenance instructions
+ - Loop diagrams
+ - SIL capability statement and proof-test procedure
+default:
+ - Factory calibration certificates
+ - Installation/operation/maintenance instructions
+ - Loop diagrams
+```
+
+## The Contractor shall submit the following closeout submittals at project completion:
+- As-installed loop diagrams and instrument index.
+- Field calibration and loop-check records.
+- Warranty documentation.
+
+```datasheet
+label: Closeout Submittals
+type: checkbox
+options:
+ - As-installed loop diagrams and instrument index
+ - Field calibration and loop-check records
+ - Warranty documentation
+default:
+ - As-installed loop diagrams and instrument index
+ - Field calibration and loop-check records
+ - Warranty documentation
+```
+
+# Quality Assurance {toc}
+
+## Temperature instruments and assemblies shall be the product of a manufacturer regularly engaged in the production of industrial temperature instrumentation.
+
+## All instruments of a given type and service shall be the product of a single manufacturer to maintain interchangeability of spare elements and transmitters.
+
+## Factory calibration shall be NIST-traceable for all RTD Class A and Class AA elements and for all instruments used in safety-instrumented functions.
+
+## Calibration shall be performed at the ice point (0°C) plus two span points bracketing the operating range.
+
+## Instruments installed in classified hazardous locations shall carry third-party certification (UL, FM, CSA, or ATEX/IECEx) appropriate to the area classification.
+
+## For safety-instrumented functions, the element and transmitter shall be certified to the required Safety Integrity Level per IEC 61511, with the proof-test interval and proof-test procedure stated on the instrument data sheet.
+
+# Environmental and Service Conditions {toc}
+
+## The Contractor shall verify that each instrument's published ambient and process temperature ratings envelope the site service conditions before procurement.
+
+## Head-mount transmitter electronics shall be rated for the connection-head ambient temperature, which for high-process-temperature service is elevated by conduction from the thermowell.
+
+## For high-process-temperature service, the connection-head ambient is elevated by conduction from the thermowell and may exceed the transmitter electronics rating; verify the ambient derating before specifying a head-mount transmitter. {note}
+
+## Where the process temperature would drive the connection-head ambient above 70°C, a remote-mount transmitter shall be used in lieu of a head-mount transmitter.
+
+## Enclosures and connection heads installed outdoors or in wash-down areas shall be rated NEMA 4X (IP66) minimum.
+
+## Instruments in Class I Division 1 locations shall be explosion-proof (NEMA 7) or protected by an approved intrinsically safe barrier.
+
+## Instruments in Class I Division 2 locations shall be intrinsically safe, non-incendive, or otherwise approved for the classification.
+
+## Process seals shall be provided at conduit entries on instruments in hazardous locations in accordance with ANSI/ISA-12.27.01 where a single seal is relied upon.
+
+```datasheet
+label: Hazardous Area Classification
+type: radio
+options:
+ - Non-hazardous (general purpose)
+ - Class I Division 2 (intrinsically safe / non-incendive)
+ - Class I Division 1 (explosion-proof or intrinsically safe)
+ - Zone 1 (Ex d or Ex ia)
+ - Zone 2 (Ex nA or Ex ic)
+default: Non-hazardous (general purpose)
+```
+
+```datasheet
+label: Enclosure / Connection Head Rating
+type: radio
+options:
+ - NEMA 4X (IP66)
+ - NEMA 4 (IP65)
+ - NEMA 7 (explosion-proof)
+ - NEMA 4X stainless steel
+default: NEMA 4X (IP66)
+```
+
+```datasheet
+label: Ambient Temperature Range
+type: range
+unit: °C
+min: -40
+max: 85
+step: 5
+```
+
+# Sensor Technology Selection {toc}
+
+## Sensor technology shall be selected on the basis of required accuracy, temperature range, and output type. {note}
+
+## An RTD shall be specified where the service requires high accuracy and long-term stability within the -200°C to +850°C range; a thermocouple shall be specified where the service exceeds the RTD range, requires fast response, or requires a rugged sheathed element in severe environments. {note}
+
+## A bimetallic dial thermometer or filled-system remote thermometer shall be specified only for local indication where no electrical output to the control system is required. {note}
+
+```datasheet
+label: Sensor Technology
+type: radio
+options:
+ - RTD (Pt100, platinum)
+ - RTD (Pt1000, platinum)
+ - Thermocouple
+ - Bimetallic dial thermometer
+ - Filled-system remote thermometer
+default: RTD (Pt100, platinum)
+```
+
+## Resistance Temperature Detectors {toc}
+
+### RTD elements shall be platinum, conforming to IEC 60751:2022 resistance-versus-temperature tables and tolerance classes.
+
+### RTD elements in field installations shall be three-wire minimum to compensate for lead resistance; two-wire RTDs shall not be used for lead runs exceeding 3 m.
+
+### RTD elements in precision and safety-instrumented service shall be four-wire to eliminate lead-resistance error entirely.
+
+### Two-wire RTD connection on field runs is a common source of uncompensated lead-resistance error and is prohibited here for that reason except for short factory-internal leads. {note}
+
+### RTD accuracy class shall be IEC 60751 Class A for industrial process control and Class B for general HVAC and building automation; Class AA shall be reserved for precision and safety-instrumented service. {note}
+
+### Class B tolerance is ±(0.30 + 0.005|t|)°C, Class A is ±(0.15 + 0.002|t|)°C, and Class AA is ±(0.10 + 0.0017|t|)°C, each evaluated at the measured temperature t in °C. {note}
+
+### RTDs used in IEC 61511 SIL 2 loops shall be Class A or better with an individual calibration certificate; Class B shall not be used for SIL-rated temperature measurement.
+
+```datasheet
+label: RTD Element Type
+type: radio
+options:
+ - Pt100, 3-wire
+ - Pt100, 4-wire
+ - Pt100, 2-wire (factory-internal leads only)
+ - Pt1000, 3-wire
+default: Pt100, 3-wire
+```
+
+```datasheet
+label: RTD Accuracy Class (IEC 60751)
+type: radio
+options:
+ - Class B (±0.30°C at 0°C) — HVAC/building automation
+ - Class A (±0.15°C at 0°C) — industrial process
+ - Class AA (±0.10°C at 0°C) — precision/SIL
+default: Class A (±0.15°C at 0°C) — industrial process
+```
+
+```datasheet
+label: RTD Operating Range
+type: range
+unit: °C
+min: -50
+max: 200
+step: 10
+```
+
+## Thermocouples {toc}
+
+### Thermocouple elements shall conform to ASTM E230/E230M for EMF tables and limits of error; IEC 60584-1 shall apply for export or global projects.
+
+### Thermocouple type shall be selected for the process temperature range and atmosphere. {note}
+
+### Type K (-200°C to 1260°C) shall be the default for general oxidizing process service; Type J (-40°C to 750°C) for reducing atmospheres; Type E (-200°C to 900°C) where the highest sensitivity is required; Type T (-200°C to 350°C) for cryogenic and food service; Type N for high-temperature oxidizing service; and noble-metal Types R and S for furnace service. {note}
+
+### Type K standard limits of error are ±2.2°C or ±0.75% of reading, whichever is greater; special limits are ±1.1°C or ±0.4%. {note}
+
+### Thermocouple extension or compensating cable shall be type-matched to the thermocouple per ISA-MC96.1; copper extension wire shall not be used with a thermocouple element.
+
+### Using copper extension wire with a thermocouple introduces a parasitic EMF error that varies with ambient temperature and corrupts the measurement; type-matched cable carries the thermoelectric reference unbroken to the cold junction. {note}
+
+### Cold-junction compensation shall be provided at a single defined location; thermocouple extension cable shall not be spliced to copper at intermediate terminal blocks ahead of the transmitter or DCS cold junction.
+
+### Where a thermocouple home run from a junction box to the marshalling cabinet would otherwise use copper, a head-mount transmitter shall be specified to convert to a 4-20 mA copper loop at the instrument.
+
+```datasheet
+label: Thermocouple Type
+type: radio
+options:
+ - Type K (-200 to 1260°C, general oxidizing)
+ - Type J (-40 to 750°C, reducing)
+ - Type E (-200 to 900°C, high sensitivity)
+ - Type T (-200 to 350°C, cryogenic/food)
+ - Type N (high-temperature oxidizing)
+ - Type R/S (noble metal, furnace)
+default: Type K (-200 to 1260°C, general oxidizing)
+```
+
+```datasheet
+label: Thermocouple Limits of Error
+type: radio
+options:
+ - Standard (±2.2°C or ±0.75%)
+ - Special (±1.1°C or ±0.4%)
+default: Standard (±2.2°C or ±0.75%)
+```
+
+```datasheet
+label: Extension / Compensating Cable
+type: select
+options:
+ - Type KX (for Type K)
+ - Type JX (for Type J)
+ - Type EX (for Type E)
+ - Type TX (for Type T)
+ - Type NX (for Type N)
+ - Copper (RTD / transmitter output only)
+default: Copper (RTD / transmitter output only)
+```
+
+## Number of Sensing Elements {toc}
+
+### Single-element assemblies shall be used for general indication and control service.
+
+### Dual-element assemblies shall be specified where redundancy is required for safety-instrumented functions, or where independent control and monitoring measurements are taken from one penetration.
+
+### Dual-element construction lets a control loop and a safety loop share one thermowell penetration without sharing a common element failure, and supports averaging or hot-standby schemes. {note}
+
+```datasheet
+label: Number of Sensing Elements
+type: radio
+options:
+ - Single element
+ - Dual element (redundant)
+default: Single element
+```
+
+# Output and Transmitter {toc}
+
+## Output and protocol shall be selected to match the control system interface and the accuracy budget. {note}
+
+## New field temperature transmitters shall provide a 4-20 mA analog output with superimposed HART revision 7 digital signal as the minimum, unless a fieldbus or wireless architecture is specified for the project.
+
+## WirelessHART output shall be limited to monitoring-only or retrofit service where wiring a new loop is impractical and the measurement is not used for closed-loop control or safety.
+
+## Local-indication-only service (bimetallic or filled-system) shall be specified where no electrical signal to the control system is required.
+
+## Transmitter total loop accuracy shall be within ±1.0°C for process control and within ±0.5°C for precision applications, including element, transmitter, and reference uncertainty.
+
+## Transmitter accuracy is typically ±0.1°C to ±0.5°C and is span-dependent; the loop accuracy budget shall account for the element tolerance class in addition to the transmitter. {note}
+
+```datasheet
+label: Output / Protocol
+type: radio
+options:
+ - 4-20 mA + HART rev 7
+ - 4-20 mA analog only
+ - WirelessHART (monitoring/retrofit)
+ - FOUNDATION Fieldbus
+ - Modbus RTU
+ - Local indication only (no electrical output)
+default: 4-20 mA + HART rev 7
+```
+
+```datasheet
+label: Transmitter Mount
+type: radio
+options:
+ - Integral / head-mount (on element connection head)
+ - Remote-mount (DIN-rail or panel)
+default: Integral / head-mount (on element connection head)
+```
+
+```datasheet
+label: Total Loop Accuracy
+type: radio
+options:
+ - ±1.0°C (process control)
+ - ±0.5°C (precision)
+default: ±1.0°C (process control)
+```
+
+## Transmitter Mounting {toc}
+
+### Integral head-mount transmitters shall be used where the connection-head ambient remains within the transmitter electronics rating, typically -40°C to +85°C.
+
+### Remote-mount transmitters shall be used where the process temperature would raise the connection-head ambient above the electronics rating, or where the element location is inaccessible for configuration and maintenance.
+
+### Ordering a head-mount transmitter for high-process-temperature service without checking the ambient derating is a recurring field failure: a 300°C process can heat the connection head above the 85°C electronics limit and cause drift or failure. {note}
+
+# Thermowells {toc}
+
+## A thermowell shall be provided for every temperature element installed in pressurized piping, process vessels, or any service where element removal under pressure or process leakage is a safety concern.
+
+## Specifying a bare RTD or thermocouple element in pressurized piping creates a personnel-safety and process-leak hazard and is prohibited; the thermowell isolates the element from the process and permits removal without breaching containment. {note}
+
+## Bare elements (no thermowell) shall be limited to duct service and other non-pressurized service such as HVAC air measurement.
+
+## Thermowell material shall be compatible with the process fluid.
+
+## 316 stainless steel shall be the default thermowell material; nickel-chromium-molybdenum alloy (UNS N10276), nickel-copper alloy (UNS N04400), nickel-chromium alloy (UNS N06600/N06625), or alumina ceramic shall be specified for corrosive or high-temperature service. {note}
+
+## Thermowell process connection rating shall match the pipe specification.
+
+## Specifying a thermowell with a lower pressure rating than the piping class (e.g., 150# flange on a 600# line) is a common RFI generator; cross-check the piping class before procurement to avoid this error. {note}
+
+```datasheet
+label: Thermowell Requirement
+type: radio
+options:
+ - Thermowell required (pressurized piping/vessel)
+ - Bare element (duct / non-pressurized)
+default: Thermowell required (pressurized piping/vessel)
+```
+
+```datasheet
+label: Thermowell Material
+type: select
+options:
+ - 316 stainless steel
+ - 304 stainless steel
+ - Nickel-chromium-molybdenum alloy (UNS N10276)
+ - Nickel-copper alloy (UNS N04400)
+ - Nickel-chromium alloy (UNS N06600)
+ - Alumina ceramic
+default: 316 stainless steel
+```
+
+```datasheet
+label: Thermowell Style
+type: radio
+options:
+ - Tapered (stepped)
+ - Straight
+ - Flanged
+ - Threaded (NPT)
+ - Socket-weld
+default: Tapered (stepped)
+```
+
+```datasheet
+label: Process Connection
+type: select
+options:
+ - 1/2" NPT male
+ - 3/4" NPT male
+ - 1" NPT male
+ - ANSI 150# flange
+ - ANSI 300# flange
+ - ANSI 600# flange
+ - Socket-weld
+default: 1/2" NPT male
+```
+
+```datasheet
+label: Process Connection Size and Rating
+type: radio
+options:
+ - 1/2" NPT (pipe ≤4", ≤600 psig)
+ - 3/4" NPT (larger pipe)
+ - Flanged ANSI 150#
+ - Flanged ANSI 300#
+default: 1/2" NPT (pipe ≤4", ≤600 psig)
+```
+
+## Wake-Frequency and Insertion Length {toc}
+
+### An ASME PTC 19.3 TW-2016 wake-frequency (Strouhal) calculation shall be submitted for every thermowell in flowing process service to confirm structural adequacy against vortex-induced resonance.
+
+### A wake-frequency calculation shall be required for all thermowells where fluid velocity exceeds 1 m/s for liquids or 10 m/s for gases.
+
+### Thermowell resonance failure in high-velocity service is a documented field failure mode in which vortex shedding excites the thermowell at its natural frequency and fatigues the root; the PTC 19.3 TW calculation governs L/D limits and the fatigue assessment. {note}
+
+### The frequency ratio of natural to shedding frequency shall be at least 1.3 for an unsupported thermowell per ASME PTC 19.3 TW; stepped or tapered thermowells shall be preferred for high-velocity service.
+
+### Thermowell insertion length shall place the tip at a minimum of 60% of the pipe inside diameter into the flow stream to limit conduction error.
+
+### The insertion-length-to-bore ratio shall satisfy L/D greater than 5 to limit conduction error along the well.
+
+### Insertion length shall be verified against the pipe inside diameter on the instrument data sheet so the well neither bottoms out nor falls short of the 60%-immersion target. {note}
+
+### A standard 6-inch-insertion thermowell bottoms out in a 2-inch pipe; insertion length versus pipe size is the single most common RFI generator in this category and shall always be checked against the pipe ID. {note}
+
+### Use the following guidance for nominal insertion length versus pipe size, subject to the wake-frequency calculation. {note}
+
+| Pipe size (NPS) | Nominal pipe ID | Target tip immersion (60% ID) | Typical insertion length (U) |
+|-----------------|-----------------|-------------------------------|------------------------------|
+| 2" | ~52 mm | ~31 mm | 2.5" (63 mm) |
+| 3" | ~78 mm | ~47 mm | 4.5" (114 mm) |
+| 4" | ~102 mm | ~61 mm | 6.0" (150 mm) |
+| 6" | ~154 mm | ~92 mm | 7.5" (190 mm) |
+| 8" | ~203 mm | ~122 mm | 10.5" (267 mm) |
+| ≥10" | per drawing | 60% of ID | per wake-frequency calculation |
+
+### For pipe smaller than 3 inches, a tapered thermowell in an elbow or a pipe expansion (tee with a larger-bore run) shall be used where straight-run immersion cannot meet the 60% target. {note}
+
+```datasheet
+label: Wake-Frequency Calculation Required
+type: radio
+options:
+ - Required (flowing process service)
+ - Not required (static / non-pressurized)
+default: Required (flowing process service)
+```
+
+```datasheet
+label: Thermowell Insertion Length (U)
+type: range
+unit: mm
+min: 50
+max: 600
+step: 10
+drawing_ref: "thermowell schedule"
+```
+
+# Element Construction and Connection Head {toc}
+
+## Element construction shall be selected for the protection-tube environment and required response time. {note}
+
+## Bare elements shall be used inside thermowells in clean, non-severe service; mineral-insulated metal-sheathed (MIMS) elements shall be used where vibration, moisture ingress, or bending is a concern; ceramic protection tubes shall be used for high-temperature furnace service. {note}
+
+## Sheath or protection-tube material shall be 316 stainless steel for general service, nickel-chromium alloy (UNS N06600 or UNS N06625) for high-temperature oxidizing service, and alumina ceramic for furnace service. {note}
+
+## The connection head shall be cast aluminum for general service and stainless steel for corrosive or wash-down service.
+
+## The conduit entry shall be sized 1/2" or 3/4" NPT to match the project wiring method.
+
+## The connection head enclosure rating shall be NEMA 4X (IP67) minimum for general process service.
+
+## The connection head enclosure rating shall be NEMA 7 for Class I Division 1 hazardous locations.
+
+```datasheet
+label: Element Construction
+type: radio
+options:
+ - Bare element (in thermowell)
+ - Mineral-insulated metal-sheathed (MIMS)
+ - Ceramic protection tube
+default: Bare element (in thermowell)
+```
+
+```datasheet
+label: Sheath / Protection Tube Material
+type: select
+options:
+ - 316 stainless steel
+ - Nickel-chromium alloy (UNS N06600)
+ - Nickel-chromium alloy (UNS N06625)
+ - Alumina ceramic
+default: 316 stainless steel
+```
+
+```datasheet
+label: Connection Head Material
+type: radio
+options:
+ - Cast aluminum (epoxy-coated)
+ - Stainless steel
+default: Cast aluminum (epoxy-coated)
+```
+
+```datasheet
+label: Conduit Entry
+type: radio
+options:
+ - 1/2" NPT
+ - 3/4" NPT
+ - M20
+default: 1/2" NPT
+```
+
+# Local Indicating Thermometers {toc}
+
+## Bimetallic dial thermometers shall conform to ASME B40.200 and shall be provided with an every-angle adjustable stem and a thermowell where installed in pressurized service.
+
+## Filled-system remote thermometers (capillary bulb and dial) shall be used where a local reading is required at a distance from the process connection that a rigid-stem dial cannot reach.
+
+## Dial size shall be selected for the required reading distance; a 3-inch dial is typical at arm's length and a 5-inch dial where the gauge must be read from a walkway or grade. {note}
+
+## Bimetallic and filled-system thermometers provide local indication only and shall not be relied upon for control or alarm functions, which require an electrical-output element and transmitter. {note}
+
+```datasheet
+label: Local Thermometer Type
+type: radio
+options:
+ - Bimetallic dial (every-angle adjustable)
+ - Filled-system remote (capillary)
+ - None (no local indication)
+default: None (no local indication)
+```
+
+```datasheet
+label: Dial Size
+type: radio
+options:
+ - 3 inch
+ - 5 inch
+default: 3 inch
+```
+
+# HVAC and Building Automation Sensors {toc}
+
+## Duct-mounted air-temperature elements shall be bare Pt100 RTDs without thermowells, with a remote-mount or transmitter output suitable for the building automation system.
+
+## Averaging elements shall be specified for supply, return, and mixed-air measurement in ducts where a single-point sensor would not represent the bulk air temperature across the duct cross-section.
+
+## A single-point sensor in a large or stratified duct cross-section can misrepresent mixed-air temperature; averaging-element length or multiple point locations shall follow ASHRAE duct-measurement guidance. {note}
+
+## Pipe-immersion RTDs for hydronic heating and chilled-water service shall be installed in thermowells in accordance with the pressurized-service requirements of this standard.
+
+## Room and space temperature sensors shall be Pt100 or Pt1000 RTDs with an enclosure and aesthetic suited to the occupied space and the building automation system interface.
+
+```datasheet
+label: HVAC Sensor Service
+type: radio
+options:
+ - Duct air (single-point)
+ - Duct air (averaging)
+ - Pipe immersion (thermowell)
+ - Room / space
+default: Duct air (averaging)
+```
+
+```datasheet
+label: Averaging Element Length
+type: range
+unit: m
+min: 0.5
+max: 7.5
+step: 0.5
+drawing_ref: "duct sensor schedule"
+```
+
+# Extension and Field Cable {toc}
+
+## RTD field wiring shall be copper, with a dedicated three-conductor (three-wire RTD) or four-conductor (four-wire RTD) twisted, shielded cable per loop.
+
+## Thermocouple field wiring ahead of any transmitter shall be type-matched compensating or extension cable per ISA-MC96.1, color-coded to the thermocouple type, twisted, shielded, and 20 AWG minimum for runs exceeding 15 m.
+
+## Cable shields shall be continuous and grounded at one end only, at the control-system end, to avoid ground loops. {note}
+
+## Armored or jacketed cable shall be provided where the field route requires mechanical protection; armor and conduit shall be bonded and grounded per NEC Article 250.
+
+```datasheet
+label: Field Cable Type
+type: radio
+options:
+ - Copper, 3-conductor twisted shielded (3-wire RTD)
+ - Copper, 4-conductor twisted shielded (4-wire RTD)
+ - Thermocouple extension/compensating, twisted shielded
+ - Copper, 2-conductor twisted shielded (transmitter output)
+default: Copper, 3-conductor twisted shielded (3-wire RTD)
+```
+
+```datasheet
+label: Cable Armor / Mechanical Protection
+type: radio
+options:
+ - Unarmored (in conduit)
+ - Interlocked armor
+ - Continuously welded armor
+default: Unarmored (in conduit)
+```
+
+# Testing {toc}
+
+## Every instrument shall be bench-calibrated and tagged before installation, with the calibration record retained for the closeout submittal.
+
+## Each loop shall be field loop-checked end to end, verifying 4 mA at the lower range value (LRV) and 20 mA at the upper range value (URV).
+
+## Thermocouple loops shall be verified for correct cold-junction compensation at ambient conditions during the loop check.
+
+## Insulation resistance of RTD elements and field cable shall be tested and recorded prior to energization.
+
+## Safety-instrumented loops shall be proof-tested per the IEC 61511 procedure stated on the instrument data sheet before the safety function is placed in service.
+
+## A loop is not accepted until the measured value at the control system agrees with a traceable reference at two points spanning the operating range within the loop accuracy budget. {note}
+
+```datasheet
+label: Field Test Scope
+type: checkbox
+options:
+ - Bench calibration and tagging
+ - End-to-end loop check (LRV/URV)
+ - Cold-junction compensation verification (TC)
+ - Insulation resistance test
+ - SIL proof test (safety loops)
+default:
+ - Bench calibration and tagging
+ - End-to-end loop check (LRV/URV)
+ - Insulation resistance test
+```
+
+# Installation {toc}
+
+## Thermowells shall be installed so that the tip reaches the required immersion depth into the flow stream and, where practical, points slightly into the flow in elbows for fastest response.
+
+## Elements shall be spring-loaded against the bottom of the thermowell to ensure thermal contact, and the annular gap shall be filled with thermal compound where the manufacturer requires it.
+
+## Connection heads shall be installed so the cover and conduit entry permit drainage and prevent moisture accumulation in the head.
+
+## Transmitters shall be installed accessible for configuration and calibration without removing the element from the thermowell.
+
+## Instruments shall be installed to permit removal of the element from the thermowell without breaking into the pressurized process.
+
+## Conduit and cable entries into connection heads in classified areas shall be sealed in accordance with NEC Article 500 and the certification of the instrument.
+
+## Metal thermowells, connection heads, and conduit systems shall be grounded and bonded in accordance with NEC Article 250.
+
+## Instrument locations, routing, and field-device arrangements shall be installed as shown. [[drawing: instrument location plan]]
+
+# Delivery, Storage, and Handling {toc}
+
+## Instruments shall be delivered in the manufacturer's original packaging with tags, calibration certificates, and protective thread or flange covers intact.
+
+## Instruments shall be stored indoors in a clean, dry, temperature-controlled environment until installation.
+
+## Thermowell bores and process threads shall be kept capped until the element is installed to prevent contamination and thread damage.
+
+## Electronic transmitters shall be protected from moisture, impact, and electrostatic discharge during storage and handling.
+
+# Warranty {toc}
+
+## The manufacturer shall warrant each instrument against defects in materials and workmanship for a minimum of 24 months from startup or 30 months from shipment, whichever occurs first.
+
+## The warranty shall cover repair or replacement of failed elements, transmitters, and thermowells, including the cost of recalibration of replacement units.
+
+```datasheet
+label: Warranty Period
+type: radio
+options:
+ - 12 months
+ - 24 months
+ - 36 months
+default: 24 months
+```
+
+# Spare Parts {toc}
+
+## The Contractor shall furnish spare sensing elements and transmitters sufficient to maintain the installed instruments without procurement delay. {note}
+
+## Spare parts shall be furnished as follows:
+- One spare element of each type, range, and accuracy class for every ten installed, minimum one of each.
+- One spare transmitter of each model and configuration for every ten installed, minimum one of each.
+- Spare thermowells for any non-standard material or process connection that is not stock.
+
+```datasheet
+label: Spare Elements (per 10 installed, min 1)
+type: range
+unit: each
+min: 0
+max: 10
+step: 1
+```
+
+```datasheet
+label: Spare Transmitters (per 10 installed, min 1)
+type: range
+unit: each
+min: 0
+max: 10
+step: 1
+```