Germanium RTDs - Technical Specifications - Lake Shore Cryotronics, Inc.

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Germanium RTDs

Specifications

Standard Curve Not applicable

Recommended excitation¹ 20 µV (0.05 K to 0.1 K); 63 µV (0.1 K to 1 K); 10 mV or less for
T > 1 K

Dissipation at recommended excitation
10^–13 W at 0.05 K, 10^–7 W at 4.2 K (temperature and model dependent)

Thermal response time 200 ms at 4.2 K,
3 s at 77 K

Use in radiation Recommended for use in ionizing radiation environments – Click here for more information

Use in magnetic field Because of their strong magnetoresistance and associated orientation effect, germanium sensors are of very limited use in magnetic fields – Click here for more information

Reproducibility² ±0.5 mK at 4.2 K

¹ Recommended excitation for T < 1 K based on Lake Shore calibration procedures using an AC resistance bridge – for more information refer to Appendix D and Appendix E
²Short-term reproducibility data is obtained by subjecting sensor to repeated thermal shocks from 305 K to 4.2 K

Range of Use³

	Minimum Limit	Maximum Limit
GR-200A	<0.05 K	100 K
GR-200B	1 K	100 K
³ The minimum/maximum range is not for individual sensors – it is the range that the GR-200A sensors cover as a group

Calibrated Accuracy

	Typical sensor accuracy⁴	Long-term stability⁵
1.4 K	±4 mK	—
4.2 K	±4 mK	±1 mK
10 K	±5 mK	—
77 K	±16 mK	±10 mK

⁴ [(Calibration uncertainty)² + (reproducibility)²] ^0.5 for more information see Appendices B, D, and E
⁵ Long-term stability data is obtained by subjecting sensor to 200 thermal shocks from 305 K to 77 K

Typical Resistance Values

GR-200 A or B	Typical resistance at 4.2 K	Suggested useful range
-30	20 W to 40 W	0.05 K to 1 K
-50	40 W to 70 W	0.1 K to 1.2 K
-100	50 W to 150W	0.3 K to 1.6 K⁷
-250	100 W to 350 W	0.5 K to 2.0 K⁷
-500	350 W to 750 W	1.0 K to 30 K⁷
-1000	750 W to 1300 W	1.4 K to 30 K⁷
-1500	1300 W to 2000 W	1.4 K to 30 K⁷
-2500	2000 W to 3000 W	4.0 K to 30 K⁷
⁷ Upper calibration temperature limit is 100 K

Typical Magnetic Field-Dependent Temperature Errors⁶ ΔT/T (%) at B (magnetic induction)

Germanium
T(K)	2.5 T	8 T	14 T
2.0	2.9	3.8	3.7
30	0.2	0.2	0.3
78	<0.1	<0.1	0.17
300	-0.1	-0.1	-0.1
⁶ Long axis of thermometer parallel to applied field

Temperature Response Data Table (typical) - See Appendix G for expanded response table
	GR-200A-30			GR-200A-50			GR-200A-100			GR-200A-250
	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)
0.05 K	25670	-34890000	-6.8	—	—	—	—	—	—	—	—	—
0.1 K	2109	-620000	-2.8	146100	-8430000	-6.2	—	—	—	—	—	—
0.2 K	346.3	-3297	-1.9	3099	-67600	-4.4	—	—	—	—	—	—
0.3 K	172.3	-891.8	-1.6	734.5	-6930	-2.8	23120	-390000	-5.2	—	—	—
0.5 K	85.69	-205.4	-1.2	244.5	-801	-1.6	3281	-20700	-3.2	29570	-221000	-3.7
1.0 K	42.41	-36.14	-0.85	98.43	-108	-1.1	534.4	-1150	-2.1	3161	-8450	-2.7
1.4 K	32.37	-17.68	-0.76	70.08	-46.5	-0.93	276.4	-353	-1.8	1376	-2220	-2.3
2.0 K	25.69	-7.316	-0.57	51.43	-20.9	-0.82	154.1	-116	-1.5	660.1	-624	-1.9
4.2 K	18.41	-1.411	-0.32	29.47	-5.09	-0.73	58.24	-16.7	-1.2	198.9	-68.9	-1.6
10 K	—	—	—	15.07	-1.18	-0.78	19.49	-2.49	-1.3	54.51	-8.22	-1.5
40 K	—	—	—	5.587	-0.133	-0.95	4.164	-0.128	-1.2	8.871	-0.303	-1.4
77.4 K	—	—	—	—	—	—	—	—	—	3.811	-0.054	-1.1
100 K	—	—	—	—	—	—	—	—	—	2.969	-0.025	-0.84

Temperature Response Data Table (typical)
	GR-200A-500			GR-200A-1000			GR-200A-1500			GR-200A-2500
	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)	R(W)	dR/dT (W/K)	(T/R)· (dR/dT)
1.4 K	8257	-19400	-3.3	21480	-55400	-3.6	25630	-64200	-3.5	76450	-213000	-3.9
2.0 K	2848	-3900	-2.7	6674	-9930	-2.9	8246	-11900	-2.9	21190	-35200	-3.3
4.2 K	520	-245	-1.9	1054	-526	-2.1	1377	-668	-2.1	2476	-1510	-2.6
10 K	88.41	-19.5	-2.2	170.9	-38.4	-2.2	238.1	-50.5	-2.1	212.4	-69.9	-3.3
40 K	5.723	-0.243	-1.7	8.289	-0.399	-1.9	14.21	-0.671	-1.9	6.959	-0.283	-1.6
77.4 K	2.231	-0.032	-1.1	2.919	-0.044	-1.2	5.011	-0.078	-1.2	2.917	-0.036	-0.96
100 K	1.751	-0.014	-0.78	2.257	-0.018	-0.82	3.846	-0.033	-0.85	2.366	-0.015	-0.63

Proper Selection of GR-200A for Use Below 1 K

Traditionally, germanium resistance thermometers have been classified according to their 4.2 K resistance value. However, for devices to be used below 1 K, there is no close correlation between the 4.2 K resistance and the suitability of the device as a thermometer. As a result, the Lake Shore low resistance germanium sensors (GR-200A-30, GR-200A-50, GR-200A-100 and GR-200A-250) are classified according to their lowest useful temperatures, not their 4.2 K resistance values.

The resistance vs. temperature behavior for these devices is typical of all the germanium sensors. As the temperature is lowered, both the resistance and sensitivity (dR/dT) increase logarithmically. The lowest useful temperature is generally limited by the rapidly increasing resistance and the difficulties encountered in measuring high resistance values.

The following recommendations are made concerning the optimum temperature range for using these devices:


GR-200A-30	0.05 K to 1.0 K
GR-200A-50	0.10 K to 1.2 K
GR-200A-100	0.3 K to 1.6 K
GR-200A-250	0.05 K to 2.0 K

The upper temperature listed is the approximate temperature where a ±0.1% resistance measurement translates into the equivalent temperature uncertainty of ±1 mK. Increasingly better temperature resolution is achievable at lower temperatures.

At the lowest temperature listed, the resistance of the sensor will fall in the range of approximately 1 kW to 100 kW In general, do not purchase a device which has a lower temperature limit than required, since some sensitivity (dR/dT) will be sacrificed at the higher temperatures. For example, a GR-200A-100 will have more sensitivity at 1 K than either a GR-200A-50 or a GR-200A-30.


Physical Specifications
	Mass	Lead type	Internal atmosphere	Sensor materials
GR-200A AA package	395 mg	4 color coded phosphor bronze with heavy build polyimide, attached with epoxy strain relief at sensor	Helium 4 (⁴He) at ≥500 W, air at <500 W	Doped germanium chip mounted strain-free in a gold plated cylindrical copper can
GR-200B B package	197 mg	4 color coded phosphor bronze with heavy build polyimide, attached with epoxy strain relief at sensor	Helium 4 (⁴He) at ≥500 W, air at <500 W	Doped germanium chip mounted strain-free in a gold plated cylindrical copper can

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