For years, you’ve relied on our 5612, 5613, and 5614 Secondary Reference Probes. These field-durable, lab-accurate PRTs have been replaced by the 5615, which comes with a NVLAP accredited calibration.
The 5615-12 is a Platinum Resistance Thermometer (PRT) with an Inconel™ 600 sheath that’s 305 mm (12 in) long and 6.35 mm (0.250 in) in diameter. It is a secondary reference temperature standard designed to bridge the gap between the highest laboratory standards and industrial or second-tier lab locations. It has short-term accuracy of ±0.013 °C at 0.01 °C.
The element is constructed of reference-grade platinum wire (99.999 % pure) for excellent stability. The wire is wound in a coil and placed in a mandrel where it’s uniformly supported in a manner that virtually eliminates hysteresis. The electrical configuration is a four-wire current-potential hookup that eliminate the effects of lead-wire resistance.
These Inconel™-sheathed probes have a fully supported sensing element, making them more durable than SPRTs. The element is protected in an ultrahigh-purity ceramic case with a hermetic glass seal to improve output stability by locking out moisture and contaminants.
This probe comes calibrated with ITS-90 coefficients, making it compatible with many excellent readout devices, including Hart’s 1529 Chub-E4, 1560 Black Stack, and 1502A Tweener. It bridges the gap between a 100-ohm industrial RTD and an SPRT.
For those needing faster thermal response, or where diameter and immersion depth are problems, order the 5615-9 or 5615-6. These probes are excellent reference probes for comparison calibrations in a Hart dry-well. The sheaths of the 5615-6 and 5615-9 are 4.76 mm (0.188 in) in diameter.
A printout of sensor resistance is provided in 1 °C increments for each probe. The 5615-9 and 5615-12 are calibrated from –196 °C to 420 °C. The 5615-6 is calibrated to 300 °C.
We’ve tested many of the probes on the market. We’ve used them in our manufacturing facility and tested them in the lab, and this is an excellent secondary standards PRT. Other instruments on the market are priced much higher, have lower stability, or are of lower quality.
Remember, these are reliable instruments and each probe comes with its own individual NVLAP-accredited calibration, lab code 200706-0.
5615-12 and 5615-9: –200 °C to 420 °C 5615-6: –200 °C to 300 °C
Nominal resistance at 0 °C
100 W ± 0.10 W
±0.013 °C at 0.010 °C
±0.01 °C at 0.010 °C
28 mm (1.1 in)
6.9 mm ± 3.3 mm from tip (0.27 in ± 0.13 in)
Sheath diameter tolerance
±0.127 mm (±0.005 in)
Minimum insulation resistance
1000 MW at 23 °C
Transition junction temperature range
–50 °C to 200 °C
Transition junction dimensions
71 mm x 13 mm dia (2.8 in x 0.5 in)
Maximum immersion length
5615-6: 102 mm (4 in) 5615-9: 178 mm (7 in) 5615-12: 254 mm (10 in)
9 seconds typical
Self heating (in 0 °C bath)
Lead-wire cable type
Teflon™ insulated with Teflon™ jacket, 22 AWG
183 cm (72 in)
Lead-wire temperature range
–50 °C to 200 °C
NVLAP-accredited calibration included, lab code 200706-0. Please see calibration uncertainty table and its explanation of changeable uncertainties.
NVLAP† Calibration Uncertainty
Expanded Uncertainty (k=2)
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 200706-0
“Accuracy” is a difficult term when used to describe a resistance thermometer. The simplest way to derive “accuracy” is to combine the probe drift specification and calibration uncertainty with readout accuracy at a given temperature.
Three thermal cycles from min to max temp, includes hysteresis, 99.9 % confidence
After 100 hrs at max temp, 99.9 % confidence
Temperatures outside this range will cause irreparable damage. For best performance, transition junction should not be too hot to touch.
Per ASTM E 644
Secondary Standard PRT, 4.76 mm x 152 mm (0.188 x 6.0 in), –200 to 300 °C
Secondary Standard PRT, 4.76 mm x 229 mm (0.188 x 9.0 in), –200 to 420 °C
Secondary Standard PRT, 6.35 mm x 305 mm (0.250 x 12.0 in), –200 to 420 °C
Probe Carrying Case
X = termination. Specify "B" (bare wire), "D" (5-pin DIN for Tweener Thermometers), "G" (gold pins), "I" (INFO-CON for 1521 or 1522 Handheld Thermometers), "J" (banana plugs), "L" (mini spade lugs), "M" (mini banana plugs), or "S" (spade lugs).