Technical reference -> thermocouples

Working principle

A thermocouple comprises an electrical circuit formed by two metal conductors of different metals soldered together at the ends. When there is a difference in temperature between the two joints, due to the Seebeck effect, a loop of current is generated and then, if one of the two joints is opened, an electromotive force (emf).
The polarization and intensity of the electromotive force depends solely on the type of metals used and the temperature to which the joints are subjected.
The joint exposed to the temperature to be measured is called the hot junction or the measuring junction while the joint between the thermocouple conductors and the measuring circuit is called the cold junction or the reference junction.
To measure a temperature with a thermocouple the reference junction must be at a given temperature (normally 0°) so that the emf generated depends solely on the temperature of the measuring junction. The type of thermocouple depends on the materials comprising the conductors which can be summarized as follows:

Type		Temperature limits (°C)	Descriptions
Symbol	Materials
S	Pt10%Rh – Pt	-50 / 1760	Thermocouples composed of noble metals (Platinum and Rhodium) enable very precise measurements to be obtained. Especially resistant at high temperatures, it is generally used in oxidizing atmospheres. It is not really recommended in reducing atmospheres or those containing metal gases.
R	Pt13%Rh – Pt	-50 / 1760	Like the “S” type thermocouple but with different percentages of the two metals.
B	Pt30%Rh – Pt6%Rh	0 / 1820	Thermocouple composed of noble metals which, due to a greater quantity of Rhodium than the “S” and “R” types, is more resistant at high temperatures and to mechanical stress.
E	Cr – Co	-270 / 1000	Thermocouple with high thermoelectrical power which combines the positive pole of the “K” type thermocouple and the negative pole of the “J” type thermocouple. Particularly indicated in oxidizing atmospheres.
J	Fe – Co	-210 / 1200	Thermocouple comprising an iron positive pole and a constantan (copper-nickel alloy) negative pole. Indicated for measuring medium temperatures in reducing atmospheres and with the presence of hydrogen and carbon. The presence of iron jeopardizes its working properly in oxidizing atmospheres.
K	Cr – Al	-270 / 1370	Thermocouple composed of alloys containing nickel. It is suitable for measuring high temperatures in oxidizing atmospheres. Not to be used in reducing atmospheres.
T	Cu – Co	-270 / 400	Thermocouple which permits accurate measurements at low temperatures in oxidizing and reducing atmospheres.
N	Nicrosil – Nisil	-270 / 400 (1) 0 / 1300 (2)	Thermocouple for high temperatures similar to type “K” but with less hysteresis.
W3	W3%Re- W25%Re	0 / 2310	Thermocouple for extremely high temperatures comprising a Tungsten positive pole containing 3% rhenium and a Tungsten negative pole containing 25% rhenium. Particularly resistant in reducing atmospheres and in the presence of hydrogen or other inert gases. Not to be used in air or oxidizing atmospheres.
W5	W5%Re – W26%Re	0 / 2310	Thermocouple very similar to W3 but with a greater percentage of rhenium which increases its mechanical resistance. Other characteristics are identical to those of the W3 thermocouple.

(1) Thermocouple with 0.32 mm diameter wires
(2) Thermocouple with 1.63 mm diameter wires

Measuring methods

The methods for carrying out measurements with thermocouples can generally be divided into two types.

The first, as shown in figure No. 1, is generally used in industrial fields where extreme precision is not necessary.

In this case the thermocouple is connected directly (fig. 1a) to the measuring device using compensated or extension cables (fig. 1b).

In this case the compensation of the reference junction is carried out directly by the measuring device which, measuring the junction temperature with other types of sensors, electronically modifies the thermocouple signal so that it is only dependent on the temperature of the measuring junction and thus the temperature to be measured.

The second type enables highly accurate measurements to be obtained and for this reason is used almost exclusively in laboratory applications.

In this case the temperature of the reference junction is maintained at a given and constant temperature (normally the melting point of ice 0°C) through manual or automatic procedures in order to compensate the electromotive force measured by the measuring device with that corresponding to the measuring junction.

Thermocouples construction

As in the case of resistance thermometers, there are also basically two construction types of thermocouples:
with traditional insulation and with mineral insulation.
The following table shows the main characteristics of the two construction types

	Response speed	Electrical Insulation	Resistance to vibrations	Resistance to pressure
Traditional Insulation	Sufficient	Good	Sufficient	Good
Mineral Insulation (MgO)	Excellent	Good	Excellent	Excellent

Traditional insulation thermocouples

Traditional insulation thermocouples comprise:

1. Measuring junction
   The measuring junction or hot junction is the area in which the two conductors of the thermocouple are joined together; since its dimensions are small, we can consider the measurement carried out with the thermocouples to be punctiform. This junction must be created in such a way that there is no mechanical stress on the two conductors (especially as regards thermocouples made of noble metals) as, once at temperature, this would jeopardize the correct functioning of the thermocouple.
2. Thermocouple wires
   The wires of the thermocouple must be of appropriate dimensions for the conditions of use; it is possible to insert two or more thermocouples into the same probe.
3. Ceramic insulators
   Ceramic insulators are used to keep the thermocouple wires insulated along the entire length of the probe both from each other and the external sheath.
4. Protective sheath
   The protective sheath is designed to protect the thermocouple wires. Since it is in contact with the process, it is important that it is made of the right material and has the right dimensions.
   The protective sheath is normally made of metal however it can be made of ceramic in the case of very high temperatures. In certain conditions is it advisable to cover the sheath with a further protective casing (thermowell).
5. Connection head
   The connection head contains the terminal board made of insulating material (normally ceramic) which permits the electrical connection of the thermocouple. Depending on the conditions of use explosionproof casing may be used.
   A 4-20mA converter can be installed instead of the terminal board.

In traditional insulation thermocouples the limits to the use of the different thermocouples is determined not only by the type of sheath but also by the dimensions of the thermocouple wires as indicated in the table below:

TYPE	CONDITIONS	WIRE DIAMETER (mm)
		3	1,5	1,3	0,8	0,5	0,25
J	Bare wires	650	480	480	425	340	310
	Sheated wires	760	590	450	480	370	370
K/N	Bare wires	1.090	925	925	870	760	700
	Sheated wires	1.260	1.090	1.090	980	870	815
T	Bare wires	315	315	260	200	200	200
	Sheated wires	370	370	315	260	200	200
E	Bare wires	760	590	590	480	370	370
	Sheated wires	870	650	650	540	425	425
S/R	Bare wires				1.540	1.480	1.320
	Sheated wires
B	Bare wires					1.700
	Sheated wires
Temperature limits in °C

Mineral insulation thermocouples

This particular construction type enables the production of high performance thermocouples with excellent mechanical characteristics. The made construction characteristics can be summarized as follows:

• the possibility of producing extremely small thermocouples (from 0.5mm diameter)
• the possibility of bending the sheath with a very sharp bending radius
• the considerable increase in the average life of the thermocouple
• the possibility of producing very long thermocouples

1. Measuring junction
   Special techniques are used to create the joint between the two conductors forming the thermocouple inside the mineral oxide insulation cable which is then closed. The measuring junction can be insulated, grounded or exposed (see table).
2. Thermocouple wires
   Inside the mineral oxide insulation cable there can be two, four or six wires; the thermocouple can thus be simple, double or triple.
3. Sheath with mineral insulation
   This comprises a metal sheath containing the conductors which are insulated from each other and from the sheath itself by extremely pure and highly compressed metal oxides; standard insulation uses magnesium oxide, MgO.
4. Connection head
   The connection head contains the terminal board made of insulating material (normally ceramic) which permits the electrical connection of the thermocouple. Depending on the conditions of use explosionproof casing may be used. A 4-20mA converter can be installed instead of the terminal board.

There are three types of measuring junction for mineral insulation thermocouples; the choice depends on the conditions of use of the thermocouple.

1. Exposed hot junction
   Characterized by very a short response time as it is in direct contact with the environment in which the temperature must be measured; however it is not recommended for use in corrosive environments.
2. Grounded hot junction
   The measuring junction is an integral part of the protective sheath and consequently the response time is quite short. This junction conforms to the ASTM-E-235 standard. It is recommended where there is high pressure (up to 3500Kg/cm2).
3. Insulated hot junction
   The hot junction is completely insulated from the protective sheath and is, therefore, particularly indicated in cases where parasitic emf could affect the measurements. This junction conforms to the ASTM-E-235 standard.

The following chart shows the time it takes a mineral insulation thermocouple to reach 63.2% of the thermal head measured in water with a speed of 0.4m/s

Main causes of errors in measurement with thermocouples

The main causes of errors which can occur while measuring the temperature with thermocouples are the following:

• Connection of thermocouple to the measuring device with an unsuitable cable
• Inversion of polarity in the connections
• Parasitic emf
• Incorrect compensation of the reference junction

All the connections between the thermocouples and the measuring devices must be carried out with suitable compensated cables. There are compensated cables for each type of thermocouple, the choice of type of insulation and dimensions depends solely on the conditions of use (see section on cables).

All compensation and/or extension cables for thermocouples have a color identifying both the type of thermocouple and its polarity. It is, therefore, important to take care not to invert the polarities in any connections.
It is, however, good practice to make as few junctions as possible in connections between thermocouples and measuring instruments and to use the special devices with compensated contacts which prevent polarity inversion.

When using thermocouples with grounded measuring junctions, parasitic emf may be introduced from the thermocouple to the measuring device and, since the thermocouple signal is in mV, it may easily be disturbed or altered.
It is, therefore, advisable to use thermocouples with insulated measuring junctions.

As stated previously measuring with thermocouples requires the compensation of the reference junction; it is important that this be carried out correctly by the measuring device.

Reference tables

Thermocouple type “B” (PtRh30% vs. PtRh6%) acc. to EN 60584-1 (ITS90)

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	-0,002	-0,003	-0,002	0,000	0,002	0,006	0,011	0,017	0,025	0
100	0,033	0,043	0,053	0,065	0,078	0,092	0,107	0,123	0,141	0,159	100
200	0,178	0,199	0,220	0,243	0,267	0,291	0,317	0,344	0,372	0,401	200
300	0,431	0,462	0,494	0,527	0,561	0,596	0,632	0,669	0,707	0,746	300
400	0,787	0,828	0,870	0,913	0,957	1,002	1,048	1,095	1,143	1,192	400
500	1,242	1,293	1,344	1,397	1,451	1,505	1,561	1,617	1,675	1,733	500
600	1,792	1,852	1,913	1,975	2,037	2,101	2,165	2,230	2,296	2,363	600
700	2,431	2,499	2,569	2,639	2,710	2,782	2,854	2,928	3,002	3,078	700
800	3,154	3,230	3,308	3,386	3,466	3,546	3,626	3,708	3,790	3,873	800
900	3,957	4,041	4,127	4,213	4,299	4,387	4,475	4,564	4,653	4,743	900
1.000	4,834	4,926	5,018	5,111	5,205	5,299	5,394	5,489	5,585	5,682	1.000
1.100	5,780	5,878	5,976	6,075	6,175	6,276	6,377	6,478	6,580	6,683	1.100
1.200	6,786	6,890	6,995	7,100	7,205	7,311	7,417	7,524	7,632	7,740	1.200
1.300	7,848	7,957	8,066	8,176	8,286	8,397	8,508	8,620	8,731	8,844	1.300
1.400	8,956	9,069	9,182	9,296	9,410	9,524	9,639	9,735	9,868	9,984	1.400
1.500	10,099	10,215	10,331	10,447	10,563	10,679	10,796	10,913	11,029	11,146	1.500
1.600	11,263	11,380	11,497	11,614	11,731	11,848	11,965	12,082	12,199	12,316	1.600
1.700	12,433	12,549	12,666	12,782	12,898	13,014	13,130	13,246	13,361	13,476	1.700
1.800	13,591	13,706	13,820								1.800
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “E” (Cr-Co) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
-200	-8,825	-9,063	-9,274	-9,455	-9,604	-9,718	-9,797	-9,835			-200
-100	-5,237	-5,681	-6,107	-6,516	-6,907	-7,279	-7,632	-7,963	-8,273	-8,561	-100
0	0,000	-0,582	-1,152	-1,709	-2,255	-2,787	-3,306	-3,381	-4,302	-4,777	0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,591	1,192	1,801	2,420	3,048	3,685	4,330	4,985	5,648	0
100	6,319	6,998	7,685	8,379	9,081	9,789	10,503	11,224	11,951	12,684	100
200	13,421	14,164	14,912	15,664	16,420	17,181	17,945	18,713	19,484	20,259	200
300	21,036	21,817	22,600	23,386	24,174	24,964	25,757	26,552	27,348	28,146	300
400	28,946	29,747	30,550	31,354	32,159	32,965	33,772	34,579	35,387	36,196	400
500	37,005	37,815	38,624	39,434	40,243	41,053	41,862	42,671	43,479	44,286	500
600	45,093	45,900	46,705	47,509	48,313	49,116	49,917	50,718	51,517	52,315	600
700	53,112	53,908	54,703	55,497	56,289	57,080	57,870	58,659	59,446	60,232	700
800	61,017	61,801	62,583	63,364	64,144	64,922	65,698	66,473	67,246	68,017	800
900	68,787	69,554	70,319	71,082	71,844	72,603	73,360	74,115	74,869	75,621	900
1.000	76,373										1.000
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “J” (Fe-Co) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
-200	-7,890	-8,095									-200
-100	-4,633	-5,037	-5,426	-5,801	-6,159	-6,500	-6,821	-7,123	-7,403	-7,659	-100
0	0,000	-0,501	-0,995	-1,482	-1,961	-2,431	-2,893	-3,344	-3,786	-4,215	0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,507	1,019	1,537	2,059	2,585	3,116	3,650	4,187	4,726	0
100	5,269	5,814	6,360	6,909	7,459	8,010	8,562	9,115	9,669	10,224	100
200	10,779	11,334	11,889	12,445	13,000	13,555	14,110	14,665	15,219	15,773	200
300	16,327	16,881	17,434	17,986	18,538	19,090	19,642	20,194	20,745	21,297	300
400	21,848	22,400	22,952	23,504	24,057	24,610	25,164	25,720	26,276	26,834	400
500	27,393	27,953	28,516	29,080	29,647	30,216	30,788	31,362	31,939	32,519	500
600	33,102	33,689	34,279	34,873	35,470	36,071	36,675	37,284	37,896	38,512	600
700	39,132	39,755	40,382	41,012	41,645	42,281	42,919	43,559	44,203	44,848	700
800	45,494	46,141	46,786	47,431	48,074	48,715	49,353	49,989	50,622	51,251	800
900	51,877	52,500	53,119	53,735	54,347	54,956	55,561	56,164	56,763	57,360	900
1.000	57,953	58,545	59,134	59,721	60,307	60,890	61,473	62,054	62,634	63,214	1.000
1.100	63,792	64,370	64,948	65,525	66,102	66,679	67,255	67,831	68,406	68,980	1.100
1.200	69,553										1.200
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “K” (Cr-Al) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
-200	-5,891	-6,035	-6,158	-6,262	-6,344	-6,404	-6,441	-6,458			-200
-100	-3,554	-3,852	-4,138	-4,411	-4,669	-4,913	-5,141	-5,354	-5,550	-5,730	-100
0	0,000	-0,392	-0,778	-1,156	-1,527	-1,889	-2,243	-2,587	-2,920	-3,243	0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,397	0,798	1,203	1,612	2,023	2,436	2,851	3,267	3,682	0
100	4,096	4,509	4,920	5,328	5,735	6,138	6,540	6,941	7,340	7,739	100
200	8,138	8,539	8,940	9,343	9,747	10,153	10,561	10,971	11,382	11,795	200
300	12,209	12,624	13,040	13,457	13,874	14,293	14,713	15,133	15,554	15,975	300
400	16,397	16,820	17,243	17,667	18,091	18,516	18,941	19,366	19,792	20,218	400
500	20,644	21,071	21,497	21,924	22,350	22,776	23,203	23,629	24,055	24,480	500
600	24,905	25,330	25,755	26,179	26,602	27,025	27,447	27,869	28,289	28,710	600
700	29,129	29,548	29,965	30,382	30,798	31,213	31,628	32,041	32,453	32,865	700
800	33,275	33,685	34,093	34,501	34,908	35,313	35,718	36,121	36,524	36,925	800
900	37,326	37,725	38,124	38,522	38,918	39,314	39,708	10,101	40,490	40,885	900
1.000	41,276	41,665	42,053	42,440	42,826	43,211	43,595	43,978	44,359	44,740	1.000
1.100	45,119	45,497	45,873	46,249	46,623	46,995	47,367	47,737	48,105	48,473	1.100
1.200	48,838	49,202	49,565	49,926	50,286	50,644	51,000	51,355	51,708	52,060	1.200
1.300	52,410	52,759	53,106	53,451	53,795	54,138	54,479	54,819			1.300
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “N” (Nicrosil – Nisil) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
-200	-3,990	-4,083	-4,162	-4,226	-4,313	-4,336	-4,345				-200
-100	-2,407	-2,612	-2,808	-2,994	-3,171	-3,336	-3,491	-3,634	-3,766	-3,884	-100
0	0,000	-0,260	-0,518	-0,772	-1,023	-1,269	-1,509	-1,744	-1,972	-2,193	0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,261	0,525	0,793	1,065	1,340	1,619	1,902	2,189	2,480	0
100	2,774	3,072	3,374	3,680	3,989	4,302	4,618	4,937	5,259	5,585	100
200	5,913	6,245	6,579	6,916	7,255	7,597	7,941	8,288	8,637	8,988	200
300	9,341	9,696	10,054	10,413	10,774	11,136	11,501	11,867	12,234	12,603	300
400	12,974	13,346	13,719	14,094	14,469	14,846	15,225	15,604	15,984	16,366	400
500	16,748	17,131	17,515	17,900	18,286	18,672	19,059	19,447	19,835	20,224	500
600	20,613	21,003	21,393	21,784	22,175	22,566	22,958	23,350	23,742	24,134	600
700	24,527	24,919	25,312	25,705	26,098	26,491	26,883	27,276	27,669	28,062	700
800	28,455	28,847	29,239	29,632	30,024	30,416	30,807	31,199	31,590	31,981	800
900	32,371	32,761	33,151	33,541	33,930	34,319	34,707	35,095	35,482	35,869	900
1.000	36,256	36,641	37,027	37,411	37,795	38,179	38,562	38,944	39,326	39,706	1.000
1.100	40,087	40,466	40,845	41,223	41,600	41,976	42,352	42,727	43,101	43,474	1.100
1.200	43,846	44,218	44,588	44,958	45,326	45,694	46,606	46,425	46,789	47,152	1.200
1.300	47,513										1.300
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “R” (PtRh13% – Pt) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
0	0,000	-0,051	-0,100	-0,145	-0,188	-0,226					0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,054	0,111	0,171	0,232	0,296	0,363	0,431	0,501	0,573	0
100	0,647	0,723	0,800	0,879	0,959	1,041	1,124	1,208	1,294	1,381	100
200	1,469	1,558	1,648	1,739	1,831	1,923	2,017	2,112	2,207	2,304	200
300	2,401	2,498	2,597	2,696	2,796	2,896	2,997	3,099	3,201	3,304	300
400	3,408	3,512	3,616	3,721	3,827	3,933	4,040	4,147	4,255	4,363	400
500	4,471	4,580	4,690	4,800	4,910	5,021	5,133	5,245	5,357	5,470	500
600	5,583	5,697	5,812	5,926	6,041	6,157	6,237	6,390	6,507	6,625	600
700	6,743	6,861	6,980	7,100	7,220	7,340	7,461	7,583	7,705	7,827	700
800	7,950	8,073	8,197	8,321	8,446	8,571	8,697	8,823	8,950	9,077	800
900	9,205	9,333	9,461	9,590	9,720	9,850	9,980	10,111	10,242	10,374	900
1.000	10,506	10,638	10,771	10,905	11,039	11,173	11,307	11,442	11,578	11,714	1.000
1.100	11,850	11,986	12,123	12,260	12,397	12,535	12,673	12,812	12,950	13,089	1.100
1.200	13,228	13,367	13,507	13,646	13,786	13,926	14,066	14,207	14,347	14,488	1.200
1.300	14,629	14,770	14,911	15,052	15,193	15,334	15,475	15,616	15,758	15,899	1.300
1.400	16,040	16,181	16,323	16,464	16,605	16,746	16,887	17,028	17,169	17,310	1.400
1.500	17,451	17,591	17,732	17,872	18,012	18,152	18,292	18,431	18,571	18,710	1.500
1.600	18,849	18,988	19,126	19,264	19,402	19,540	19,677	19,814	19,951	20,087	1.600
1.700	20,222	20,356	20,488	20,620	20,749	20,877	21,003				1.700
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “S” (PtRh10% – Pt) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
0	0,000	-0,053	-0,103	-0,150	-0,194	-0,236					0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,055	0,113	0,173	0,235	0,299	0,365	0,433	0,502	0,573	0
100	0,646	0,720	0,795	0,872	0,950	1,029	1,110	1,191	1,273	1,357	100
200	1,441	1,526	1,612	1,698	1,786	1,874	1,962	2,052	2,141	2,232	200
300	2,323	2,415	2,507	2,599	2,692	2,786	2,880	2,974	3,096	3,164	300
400	3,259	3,355	3,451	3,548	3,645	3,742	3,840	3,938	4,036	3,134	400
500	4,233	4,332	4,432	4,532	4,632	4,732	4,833	4,934	5,035	5,137	500
600	5,239	5,341	5,443	5,546	5,659	5,753	5,857	5,961	6,065	6,170	600
700	6,275	6,381	6,486	6,593	6,699	6,806	6,913	7,020	7,128	7,236	700
800	7,345	7,454	7,563	7,673	7,783	7,893	8,003	8,114	8,226	8,337	800
900	8,449	8,562	8,674	8,787	8,900	9,014	9,128	9,242	9,357	9,472	900
1.000	9,587	9,703	9,819	9,935	10,051	10,168	10,285	10,403	10,520	10,638	1.000
1.100	10,757	10,875	10,994	11,113	11,232	11,351	11,471	11,590	11,710	11,830	1.100
1.200	11,951	12,071	12,191	12,312	12,433	12,554	12,675	12,796	12,917	13,038	1.200
1.300	13,159	13,280	13,402	13,523	13,644	13,766	13,887	14,009	14,130	14,251	1.300
1.400	14,373	14,494	14,615	14,736	14,857	14,978	15,099	15,220	15,341	15,461	1.400
1.500	15,582	15,702	15,822	15,942	16,062	16,182	16,301	16,420	16,539	16,658	1.500
1.600	16,777	16,895	17,013	17,131	17,249	17,366	17,483	17,600	17,717	17,832	1.600
1.700	17,947	18,061	18,174	18,825	18,395	18,503	18,609				1.700
°C	0	10	20	30	40	50	60	70	80	90	°C

Reference junction at 0°C

Thermocouple type “T” (Cu-Co) acc. to EN 60584-1 (ITS 90)

°C	0	-10	-20	-30	-40	-50	-60	-70	-80	-90	°C
	FEM thermoelectric voltage in mV
-200	-5,603	-5,753	-5,888	-6,007	-6,105	-6,180	-6,232	-6,258			-200
-100	-3,379	-3,657	-3,923	-4,177	-4,419	-4,648	-4,865	-5,070	-5,261	-5,439	-100
0	0,000	-0,383	-0,757	-1,121	-1,475	-1,819	-2,153	-2,476	-2,788	-3,089	0

°C	0	10	20	30	40	50	60	70	80	90	°C
	FEM thermoelectric voltage in mV
0	0,000	0,391	0,790	1,196	1,612	2,036	2,468	2,909	3,358	3,814	0
100	4,279	4,750	5,228	5,714	6,206	6,704	7,209	7,720	8,237	8,759	100
200	9,288	9,822	10,362	10,907	11,458	12,013	12,574	13,139	13,709	14,283	200
300	14,862	15,445	16,032	16,624	17,219	17,819	18,422	19,030	19,641	20,255	300
400	20,872										400

Reference junction at 0°C

Tolerances and appliances limits

TYPE	JIS C 1602			ANSI MC 96.1			DIN 43710		EN 60584-2
	Temp. range (°C)	Grade	Tolerance (°C)	Temp. range (°C)	Grade	Tolerance (°C)	Temp. range (°C)	Tolerance (°C)	Temp. range (°C)	Grade	Tolerance (°C)
B	+200+1700	0.5	± 4°C or ± 0.5%	+800+1700	STD	± 0.5%	–	–	+600+1700	2	± 0.0025*|t|
										3	± 4°C or ± 0.005* |t|
R	0+1600	0.25	± 1.5°C or ± 0.25%	0+1450	STD	± 1,5°C or ± 0,25%	0+600	± 3°C	0-1600	1	± 1°C or ± [1+0.003 * (T-1100)]°C
					SPC	± 0,6°C or ± 0,1%	+600+1600	± 5°C		2	± 1,5°C or ± 0.0025 * |t|
S	0+1600	0.25	± 1.5°C or ± 0.25%	0+1450	STD	± 1,5°C or ± 0,25%	0-600	± 3°C	0-1600	1	± 1°C or ± [1+0.003 * (T-1100)]°C
					SPC	± 0,6°C or ± 0,1%	600-1600	± 5°C		2	± 1,5°C or ± 0.0025* |t|
K	0+1000	0.4	± 1.5°C or ± 0.4%	0+1250	STD	± 2.2°C or ± 0.75%	0+400	± 3°C	-40+1000	1	± 1,5°C or ± 0.004* |t|
							400+1200	± 0.75°C
	0+1200	0.75	± 2.5°C or ± 0.75%		SPC	± 1.1°C or ± 0.40%			-40+1200	2	± 2,5°C or ± 0.0075* |t|
	-200-0	1.5	± 2.5°C or ± 1.5%	-200-0	STD	± 2.2°C or ± 2%			-200+40	3	± 2,5°C or ± 0.015* |t|
N	0+1000	0.25	± 1.5°C or ± 0.4%	0+1250	STD	± 2.2°C or ± 0.75%	–	–	-40+1000	1	± 1,5°C or ± 0.004* |t|
	0+1200	0.75	± 2.5°C or ± 0.75%		SPC	± 1.1°C or ± 0.40%			-40+1200	2	± 2,5°C or ± 0.0075* |t|
	-200-0	1.5	± 2.5°C or ± 1.5%	-200-0	STD	± 2.2°C or ± 2%			-200+40	3	± 2,5°C or ± 0.015* |t|
E	0+800	0.4	± 1.5°C or ± 0.4%	0+900	STD	± 1,7°C or ± 0.50%	–	–	-40-800	1	± 1,5°C or ± 0.004* |t|
		0.75	± 2.5°C or ± 0.75%		SPC	± 1°C or ± 0.40%			-40-900	2	± 2,5°C or ± 0.0075* |t|
	-200-0	1.5	± 2.5°C or ± 1.5%	-200-0	STD	± 1.7°C or ± 1%			-200-40	3	± 2,5°C or ± 0.015* |t|
J	0+750	0.4	± 1.5°C or ± 0.4%	0+750	STD	± 2.2°C or ± 0.75%	0.400	± 3°C	-40+750	1	± 1,5°C or ± 0.004* |t|
		0.75	± 2.5°C or ± 0.75%		SPC	± 1.1°C or ± 0.4%	400+900	± 0.75°		2	± 2,5°C or ± 0.0075* |t|
T	0+350	0.4	± 0.5°C or ± 0.4%	0+350	STD	± 0.5°C or ± 0.4%	-200+400	± 3°C	-40+350	1	± 0,5°C or ± 0.004* |t|
		0.75	± 1°C or ± 0.75%		SPC	± 1°C or ± 0.75%				2	± 1°C or ± 0.0075* |t|
	-200-0	1.5	± 1°C or ± 1.5%	-200-0	STD	± 1°C or ± 1.5%			-200+40	3	± 1°C or ± 0.015* |t|