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Fluke 5609-300-B Secondary Standard PRT with Calibration Option

Fluke 5609-300-B
Catalog #: 3056803
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PROBE, SECON. PRT, 100 OHM (6 X 300 MM)
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  • 5609-300-B (bare wire)
  • 300 millimeters x 6 millimeters
  • Very stable thermometer from 200 °C to 670 °C (100 mm minimum immersion)
  • Dry-well reference with 90 ° bend
  • Calibration not included, NVLAP-accredited calibration optional, lab code 200348-0
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List Price: $930.00
Sale: $837.00
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Product Information

5609-300-B  Secondary Standard PRT,  300 mm x 6 mm, –200 to 670 °C

If you want a very stable thermometer from –200 °C to 670 °C and are particular about the calibration, then look no further than our 5609 Secondary Reference PRT. Its short-term stability at the triple point of water is only ± 7 mK and its one-quarter inch (6.23mm) diameter lets you get accurate measurements in only 100 mm of immersion.

The 5608 is also a ± 7 mK probe at the triple point of water, but its one-eighth inch (3.18 mm) diameter gets you accurate measurements from –200 °C to 500 °C with only 80mm (3.1 in) of immersion. With multiple sheath length options on both of these probes, you can find the dimensions that are just right for your specific application.

The 5608 comes with a one-eighth inch (3.18 mm) diameter sheath in lengths of 9 inches or 12 inches. The 5609 comes with a one-quarter inch (6.35 mm) diameter sheath in lengths of 12 inches, 15 inches, and 20 inches; or with a 6 mm diameter in lengths of 300 mm, 400 mm, or 500 mm.

When looking for improved response time and reduced stem effect in shallow immersion, look for small diameter probes, because the measurement error called stem effect is caused by the diameter of the stem rather than the length of the stem.

Both of these probes have Inconel™ sheaths and are made using a special manufacturing process, giving them great precision over a wide temperature range. The sensors for these probes are reference-grade platinum and feature four-wire connections with less noisy measurements than two-wire counterparts.

These probes come with a certificate of compliance to ensure the meet their specifications. If you’d like, you can also order a NVLAP-accredited calibration from our laboratory, lab code 200348-0. On the report of calibration, you’ll get the test data and the ITS90 calibration coefficients that you can easily input into any Fluke Calibration thermometer. If you order your probe with an smart connector, we’ll program the coefficients directly into your connector, which loads the coefficients for you when you plug it into our 1524 Handheld Thermometer.


Temperature range 5608: –200 °C to 500 °C 5609: –200 °C to 670 °C
Nominal resistance at 0.01 °C 100 Ω ± 0.5 Ω
Temperature coefficient 0.0039250 Ω/Ω/°C
Relative Accuracy[1] ± 0.007 °C at –200 °C
± 0.008 °C at 0 °C
± 0.020 °C at 420 °C
± 0.027 °C at 660 °C
Short-term repeatability[2] ± 0.007 °C at 0.010 °C
± 0.013 °C at max temp
Drift[3] ± 0.01 °C at 0.010 °C
± 0.02 °C at max temp
Hysteresis ± 0.01 °C maximum
Sensor length 30 mm ± 5 mm (1.2 in ± 0.2 in)
Sensor location 3 mm ± 1 mm from tip (0.1 in ± 0.1 in)
Sheath material Inconel™ 600
Minimum insulation resistance 5608: 500 MΩ at 23 °C, 20 MΩ at 500 °C
5609: 500 MΩ at 23 °C, 10 MΩ at 670 °C
Transition junction temperature range[4] –50 °C to 200 °C
Transition junction dimensions 71 mm x 12.5 mm (2.8 in x 0.49 in)

Minimum immersion length[5]     (<5 mK error)

5608: 80 mm (3.1 in)
5609: 100 mm (3.9 in)
Maximum immersion length 305 mm (12 in)
Response time[5] 5608: 9 seconds typical
5609: 12 seconds typical
Self heating (in 0 °C bath) 5608: 75 mW/°C
5609: 50 mW/°C
Lead-wire cable type PTFE 24 AWG
Lead-wire length 1.8 m (6 ft)
Lead-wire temperature range –50 °C to 250 °C

Calibration not included; NVLAP-accredited calibration optional, lab code 200348-0. Please see calibration uncertainty table and its explanation of changeable uncertainties.

[1] Includes short-term repeatability and 100 hr drift. Calibration will add additional uncertainties.

[2] Three thermal cycles from min to max temp, includes hysteresis, 95 % confidence (k=2)

[3] After 100 hours at max temp, 95 % confidence (k=2)

[4] Temperatures outside this range will cause irreparable damage. For best performance, transition junction should not be too hot to touch.

[5] Per ASTM E 644
Calibration Uncertainty for optional NVLAP-accredited† calibration
Temperature Expanded Uncertainty (k=2)
–200 °C 0.025 °C
–100 °C 0.025 °C
–40 °C 0.025 °C
0 °C 0.025 °C
156 °C 0.025 °C
230 °C 0.030 °C
420 °C 0.045 °C
660 °C 0.050 °C
Note: Calibration uncertainties depend on the uncertainties of the lab performing the calibration. Subsequent calibrations of this probe performed with different processes, at different facilities, or with changed uncertainty statements may state different uncertainties. †Lab code 200348-0

Fluke 5609-300-B Product Specifications Summary:
(for full specs please see the full specs tab or the data sheet)

Accessories/Probes/Temperature Probes Template

Test Equipment General Attributes


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