R Type Thermocouple vs S Type Thermocouple: Which Is Better, and Why India’s High-Temperature Industries Are Choosing R Type
Walk into any glass melting facility in Firozabad, Bharuch, or Nashik, talk to an instrumentation engineer in a steel soaking pit in Bhilai or Jamshedpur, or speak to a calibration lab technician at a NABL-accredited facility in Bengaluru or Pune — and you’ll find a recurring debate: R type or S type thermocouple? Both are platinum-rhodium noble metal thermocouples. Both cover broadly similar temperature ranges. Both are specified under the same ANSI MC 96.1 calibration standard. So which is actually better, and when should each be chosen?
This guide answers that question completely — with the full specification of Aavad’s ARWS R Type Thermocouple, a side-by-side comparison of R vs S, and a comprehensive map of Indian industries and applications where R type is the preferred or required specification.
What Is an R Type Thermocouple?
A Type R thermocouple is a noble metal thermocouple built from:
- Positive leg: 87% Platinum + 13% Rhodium (Pt.Rh 13%)
- Negative leg: Pure Platinum (Pt)
The 13% rhodium content in the positive leg is the defining difference from the S type (which uses 10% rhodium). This 3% additional rhodium gives Type R its characteristic performance profile.
Per Aavad’s own product specification: “Type R thermocouples are usable up to 1,480°C (2,700°F). They are extremely stable but reducing atmospheres are particularly damaging. Type R thermocouples cover similar applications as Type S, but offer improved stability and a marginal increase in range. Consequently, Type R tends to be used in preference to Type S.”
Full Specifications: Aavad ARWS R Type Thermocouple
| Parameter | Specification | Engineering Significance |
|---|---|---|
| Make | Aavad (AAVAD) | ISO 9001:2015 |
| Model | ARWS | Standard R Type ceramic assembly |
| SKU | ARWS-S-650 | Catalogue reference |
| Element | Pt.Rh (13%)/Pt | Platinum-13% Rhodium/Platinum noble metal pair |
| Element diameter | 0.30 mm | Standard noble metal wire gauge |
| Calibration standard | ANSI MC 96.1 | International accuracy compliance |
| Configuration | Simplex | Single element, 2-wire output |
| Insulation | Twin hole ceramic Ker-710 | K-99, Alumina 99.7% — highest purity standard |
| Hot junction | Un-grounded | Electrically isolated — no furnace ground interference |
| Terminal block | Ceramic with nickel-plated brass terminals | High-temperature terminal construction |
| Head | Die-cast aluminum weatherproof ANSI Blue, threaded cover & chain | IP-67 rated |
| Protection class | IP-67 | Sealed against dust and water ingress |
| Cable entry | 1/2″ (F) NPT | Standard cable entry |
| Holding tube MOC | SS 310 | High-temperature stainless transition tube |
| Holding tube diameter | 21 mm | Standard noble metal holding tube OD |
| Holding tube length | 150 mm | Metallic section length |
| Ceramic tube length | 500 mm | Total ceramic zone length |
| No. of protection | Single protection | Single Ker-710 outer ceramic protection tube |
| Outer ceramic diameter | 15 × 18 mm, Ker-710 (k-99, alumina 99.7%) | High-purity alumina single ceramic protection |
| Joint construction | High-temperature alumina compound bonding | Structural integrity at the ceramic-to-metal joint |
| Range | Up to 1,480°C (2,700°F) | R type rated continuous operating range |
| Datasheet | ARIS_21X500 | Available for download from product page |
R Type vs S Type: The Definitive Comparison
This is the question every engineer asks before their first noble metal thermocouple purchase. Here it is answered precisely:
| Parameter | R Type (Pt.Rh 13%/Pt) | S Type (Pt.Rh 10%/Pt) |
|---|---|---|
| Positive leg rhodium % | 13% | 10% |
| Continuous temperature range | Up to 1,480°C | Up to 1,600°C |
| Long-term stability | Better than S type — higher Rh content improves long-term stability | Very good, but slightly lower than R type at equivalent temperatures |
| Third-party calibration support | Excellent — widely calibrated | Even more widely calibrated — ITS-90 reference type |
| Historical preference | European and process industries often prefer R type | More widely used in the US and internationally as the ITS-90 standard |
| Sensitivity (output signal) | Slightly lower EMF output than S type | Marginally higher EMF output than R type |
| Cost | Similar — both use platinum and platinum-rhodium | Similar |
| Best for | Applications prioritizing long-term stability; many European glass and steel standards | Applications requiring the widest third-party calibration support; pharmaceutical validation reference measurement |
The practical bottom line: R type offers improved long-term stability and a slightly higher range compared to S type due to its higher rhodium content. S type provides a broader calibration base and a marginally higher continuous temperature ceiling (1,600°C vs 1,480°C). For applications up to 1,480°C where long-term stability is the priority — the majority of glass furnace, steel, and ceramics applications — R type is the preferred specification. For applications specifically requiring the ITS-90 reference standard (pharmaceutical validation, calibration lab reference), S type’s historical role as the ITS-90 reference instrument gives it specific advantages.
Why Ker-710 (99.7% Alumina) Makes the ARWS Stand Apart from Lower-Grade Alternatives
The single-protection ceramic tube on the ARWS uses Ker-710 alumina 99.7% (k-99) — not the Ker-610 alumina/mullite ceramic used in the entry-level Furnace Crown Thermocouple (ARWS-S-1). This distinction matters for service life:
- Ker-710 (99.7% alumina) is specifically formulated for noble metal protection — chemically inert toward platinum and platinum-rhodium conductors, with minimal silica or oxide impurity content that could contaminate the noble metal elements at sustained high temperatures
- Ker-610 (alumina/mullite) contains higher levels of silica and other oxides that can gradually diffuse through the ceramic wall and contaminate platinum elements, reducing service interval at the upper end of the operating range
For the ARWS’s 1,480°C rated service in high-temperature process environments, Ker-710 is the correct specification — it provides the chemical purity and thermal stability that protects the expensive platinum-rhodium element throughout the sensor’s service life.
How R Type Compares to B Type
| Parameter | R Type (ARWS) | B Type (ABHS) |
|---|---|---|
| Rhodium content | 13% in positive leg only | 30% positive + 6% negative |
| Maximum continuous range | 1,480°C | 1,700°C |
| Minimum usable temperature | Can be used from ambient | Not suitable below ~600°C |
| Best for | Standard high-temperature industrial measurement up to 1,480°C | Applications specifically exceeding R/S type ceiling; specialist ultra-high-temp |
R type is the correct specification for the large majority of high-temperature industrial applications up to 1,480°C. B type is specified only when process temperatures regularly exceed 1,480°C and justify its higher cost and operating restrictions.
Industries and Applications Across India
Glass Manufacturing
All India glass clusters: Firozabad, Agra (UP) | Bharuch, Surat, Vapi (Gujarat) | Nashik (Maharashtra) | Kolkata, Howrah (WB) | Hyderabad (Telangana) | Bhiwadi (Rajasthan) | Sriperumbudur (Tamil Nadu)
R type thermocouples are widely used in glass furnace crown monitoring, combustion space temperature monitoring, and process control applications where temperatures reach 1,200°C–1,450°C. Many European glass industry standards and glass plant engineering specifications default to R type over S type — a preference that Indian glass plants with European engineering partnerships often follow.
Steel and Iron Metallurgy
Hubs: Jamshedpur (Tata Steel, Jharkhand) | Bhilai (SAIL, CG) | Rourkela (SAIL, Odisha) | Durgapur (SAIL, WB) | Bokaro (SAIL, Jharkhand) | Hospet/Vijayanagar (JSW, Karnataka) | Visakhapatnam (RINL, AP) | Hazira, Surat (Gujarat)
Soaking pit and reheating furnace temperature monitoring, continuous casting tundish temperature control, and heat-treatment furnace zone monitoring across India’s integrated and mini steel plants.
Ceramics, Tiles, and Refractory Industry
Hub: Morbi, Rajkot, Wankaner (Gujarat) — India’s ceramics manufacturing cluster | Jabalpur, Katni (MP — refractory manufacturers) | Belagavi (Karnataka)
Tunnel kiln firing zone monitoring at peak temperatures, periodic spot-check calibration reference measurements, and process control for advanced ceramics production.
Cement Industry — Burning Zone and High-Temperature Zones
Hubs: Chittorgarh, Beawar (Rajasthan) | Nalgonda, Yerraguntla (AP) | Gulbarga (Karnataka) | Porbandar (Gujarat) | Jabalpur (MP)
Rotary kiln burning zone temperatures, preheater cyclone monitoring, and cooler hot-zone measurement in cement manufacturing.
Petrochemical and Refinery Fired Heaters
Hubs: Jamnagar (Reliance/HPCL Gujarat) | Vadodara (IOCL) | Visakhapatnam (HPCL) | Mangaluru (MRPL) | Chennai (CPCL) | Mumbai (BPCL)
High-temperature combustion zone monitoring in process furnaces and reformers where temperatures approach or exceed base-metal thermocouple limits.
Calibration Laboratories and Reference Measurement
NABL-accredited labs across India | NPL New Delhi | CSIR labs | BARC Trombay | ISRO Bengaluru
R type thermocouples serve as calibration transfer standards and reference instruments for high-temperature measurement, typically used alongside S type references in multi-point calibration protocols.
Power Generation
Hubs: Korba (CG) | Singrauli, Satpura (MP) | Ramagundam (AP) | Ennore, Tuticorin (TN) | Gandhinagar, Wanakbori (Gujarat) | Chandrapur (Maharashtra)
Superheater and reheater temperature monitoring, combustion zone measurement, and heat recovery monitoring at large thermal power stations.
Aerospace, Defence, and Research
Hubs: Bengaluru (ISRO, HAL, DRDO, NAL) | Thiruvananthapuram (VSSC) | Hyderabad (DRDL) | Pune (ARDE) | Trombay (BARC)
High-temperature material testing, propulsion test rig instrumentation, and research furnace monitoring.
India-Wide Coverage
Aavad Instrument supplies R Type Thermocouples PAN India from Ahmedabad, Gujarat:
Gujarat: Ahmedabad, Vadodara, Surat, Rajkot, Morbi, Bharuch, Jamnagar, Vapi, Ankleshwar, Dahej, Gandhinagar, Hazira, Porbandar, Bhavnagar, Wankaner
Maharashtra: Nashik, Pune, Mumbai, Aurangabad, Nagpur, Chandrapur, Raigad
UP: Firozabad, Agra, Noida, Kanpur, Lucknow, Renukoot
WB: Kolkata, Howrah, Durgapur, Asansol, Bardhaman, Haldia
Rajasthan: Jaipur, Chittorgarh, Beawar, Kota, Alwar, Bhiwadi, Neemrana, Bhilwara
Tamil Nadu: Chennai, Coimbatore, Mettur, Ennore, Hosur, Tuticorin, Sriperumbudur
Karnataka: Bengaluru, Ballari/Hospet, Belagavi, Mysuru, Mangaluru, Gulbarga
Telangana & AP: Hyderabad, Ramagundam, Kothagudem, Visakhapatnam, Nalgonda, Kadapa
Odisha: Bhubaneswar, Rourkela, Angul, Hirakud, Talcher, Paradip, Sambalpur
Jharkhand: Jamshedpur, Bokaro, Ranchi, Dhanbad
Chhattisgarh: Raipur, Bhilai, Korba, Raigarh | MP: Indore, Bhopal, Jabalpur, Singrauli
Delhi NCR: Delhi, Noida, Gurugram, Faridabad, Ghaziabad
Haryana: Gurugram, Manesar, Panipat, Faridabad
Punjab: Ludhiana, Amritsar, Mohali, Jalandhar
Kerala: Kochi, Thiruvananthapuram, Thrissur, Kozhikode
HP & Uttarakhand: Baddi, Nalagarh, Haridwar, Roorkee, Kashipur
Goa: Panaji, Vasco, Ponda | Assam: Guwahati, Numaligarh, Dibrugarh
Aavad Instrument: India’s #1 R Type Thermocouple Manufacturer
Aavad Instrument Pvt. Ltd., Chandkheda, Ahmedabad, Gujarat:
- ISO 9001:2015 certified | NABL-accredited calibration laboratory
- 15+ years | 38M+ installations | 2,900+ customers | 12+ countries
- Trusted by BHEL, ONGC, HAL, BARC, NALCO, NPCIL, L&T, MIDHANI, Indian Railways, Indian Oil, Bharat Petroleum, RVUN, Piramal Glass, Saint-Gobain, Cera, Aditya Birla Group, Torrent Pharma
- Complete Ceramic Tube Thermocouple Manufacturer category
Frequently Asked Questions
Q1. Is R type thermocouple better than S type?
Per Aavad’s product specification and widely accepted industry practice: R type thermocouples offer improved long-term stability and a marginal increase in operating range compared to S type, owing to their higher rhodium content (13% vs 10%). For most industrial applications up to 1,480°C — glass furnaces, steel plants, ceramics kilns — R type is consequently used in preference to S type. S type’s specific advantage is its historical role as the ITS-90 temperature scale reference standard, which makes it the preferred choice for calibration laboratory reference instruments and pharmaceutical validation where ITS-90 traceability is specifically documented.
Q2. What is the maximum temperature of Aavad’s R Type Thermocouple (ARWS)?
The ARWS is rated for continuous operation up to 1,480°C (2,700°F).
Q3. Why does R type use Ker-710 (99.7% alumina) ceramic insulation?
Ker-710 alumina 99.7% is specifically selected for noble metal protection tube service — its high purity ensures minimal silica and oxide impurity content that could contaminate the platinum-rhodium conductors at sustained high temperatures. Lower-purity ceramics would introduce contamination that permanently degrades the R type thermocouple’s calibration over its service life.
Q4. Why must R type thermocouples never be used in reducing atmospheres?
The platinum and platinum-rhodium elements in R type thermocouples are vulnerable to contamination from carbon monoxide, hydrogen, and other reducing gases — these diffuse through the ceramic protection at extreme temperatures and react with the noble metal conductors, permanently altering their thermoelectric properties. R type must only be used in oxidizing or inert atmospheres.
Q5. How does R type thermocouple work — what is its sensing principle?
R type thermocouples work on the Seebeck effect — a small voltage (EMF) is generated at the junction between the Pt.Rh 13% and pure Pt conductors that is proportional to the temperature difference between the hot junction (at the sensing tip) and the reference (cold) junction at the terminal block. This voltage is read by a temperature controller or indicator calibrated to the ANSI MC 96.1 Type R EMF–temperature table to display the measured temperature.
Q6. What is the difference between R type ARWS-S-650 and the Furnace Crown ARWS-S-1?
Both are R type (Pt.Rh 13%/Pt) assemblies, but with different ceramic specifications. The ARWS (R Type, ARWS-S-650) uses Ker-710 (99.7% alumina) and has a 500mm ceramic tube, rated to 1,480°C. The Furnace Crown (ARWS-S-1) uses Ker-610 (alumina/mullite) with a 450mm ceramic tube, rated to 1,450°C — the entry-level crown assembly for standard glass furnace monitoring applications.
Q7. Is NABL calibration available for R Type Thermocouples?
Yes — Aavad’s in-house NABL-accredited calibration laboratory issues traceable calibration certificates for R type thermocouples, providing the documentation required for ISO quality systems, regulatory audits, and precision measurement applications.
Q8. Does Aavad supply R Type Thermocouples PAN India including all major high-temperature industry clusters?
Yes — PAN India from Ahmedabad, with active supply to all major glass manufacturing (Firozabad, Bharuch, Nashik, Kolkata), steel (Jamshedpur, Bhilai, Rourkela, Durgapur, Hospet), ceramics (Morbi, Jabalpur), cement (Chittorgarh, Nalgonda), petrochemical (Jamnagar, Visakhapatnam), and research/defence (Bengaluru, Hyderabad, Trombay) hubs across India.
Buy R Type Thermocouples from India’s #1 Manufacturer
View the product page and download datasheet ARIS_21X500 or contact Aavad Instrument for a quote.
📞 +91 90996 22823 | ✉ hrg@aavadinstrument.com | ISO 9001:2015 | NABL Accredited | Ahmedabad, Gujarat | PAN India Supply
