<strong>Very stable thermometer from –200 °C to 670 °C</strong>
<ul>
 	<li>5608: –200 °C to 500 °C (80 mm minimum immersion)</li>
 	<li>5609: –200 °C to 670 °C (100 mm minimum immersion)</li>
 	<li>Calibration not included, NVLAP-accredited calibration optional, lab code 200348-0</li>
 	<li>Dry-well reference with 90 ° bend</li>
</ul>
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.