Fluke Calibration 9173 Metrology Well

Key features

Exceptional stability (±0.005 °C) and axial uniformity (±0.02 °C over a 60 mm zone).
Immersion depth to 203 mm (8 in)
Optional ITS-90 reference input reads PRTs to ±0.006 °C
Wide Temperature range from –45 °C to 700 °C

Download the product manual Download the data sheet

Product overview: Fluke Calibration 9173 Metrology Well

Display Accuracy

Most dry-wells are calibrated by inserting a calibrated PRT and adjusting internal control sensors. However, this approach has limited value due to:

Differences between the reference PRT and thermometers being tested
Thermal gradients in the block
Inadequate immersion from short blocks

Metrology Wells overcome these issues through:

Minimized temperature gradients, loading effects, and hysteresis
Calibration using traceable, accredited PRTs
Proprietary electronics with repeatable accuracy, exceeding specs by more than 10x
Display accuracy from ±0.1 °C (typical temps) to ±0.25 °C at 661 °C

An application note is available to better understand the associated uncertainties.

Optional: For improved accuracy, Metrology Wells can be ordered with built-in electronics for external PRT reading using ITS-90 characterizations.

Stability

Fluke heat sources are among the most stable in the world—and Metrology Wells improve upon this legacy:

Models 9170 / 9171: Stability of ±0.005 °C over the full range
Model 9173 (700 °C unit): Stability of ±0.03 °C

Only fluid baths or primary fixed-point devices offer better performance. This level of stability cannot be matched by the “off-the-shelf” controllers found in most dry-wells.

Axial Uniformity

According to EA-10/13 guidelines, dry-wells should have a 40 mm zone of maximum homogeneity. Metrology Wells go further with:

Dual-zone control
Increased well depth
Homogeneous zones extending 60 mm (2.36 in)
Vertical gradients ranging from ±0.02 °C at 0 °C to ±0.4 °C at 700 °C

Specifications for axial uniformity are published and guaranteed for each unit.

Radial Uniformity

Defined as the temperature difference between wells:

Metrology Wells use a strict definition—largest difference between homogeneous zones of wells ≤6.4 mm (0.25 in) in diameter
Models 9170 / 9171 (cold units): ±0.01 °C
Models 9172 / 9173 (hot units): ±0.01 °C to ±0.04 °C at 700 °C

Poorly designed sources or use of large probes can lead to large variations; Metrology Wells prevent this.

Loading Effects

Loading is the temperature shift when all wells are filled versus when only one is. Metrology Wells minimize this through:

Deep well design
Dual-zone controls
Cold units show minimal effects, as low as ±0.005 °C

Hysteresis

Thermal hysteresis arises mostly from internal control sensors rather than high-quality reference PRTs. It reflects the difference in measurements at the same set point approached from different directions.

More pronounced near midpoints of temperature ranges
Metrology Wells use better internal components
Hysteresis effects range from 0.025 °C to 0.07 °C

Immersion Depth

Deep immersion is key to minimizing axial gradient and loading effects. Metrology Wells accommodate sensor-specific factors such as:

Sensor location and size
Probe mass and width
Lead wire configuration

Well depths:

Models 9171 / 9172 / 9173: 203 mm (8 in)
Model 9170: 160 mm (6.3 in), enabling performance to –45 °C

User Interface and Software Features

Metrology Wells are simple and intuitive to use, featuring:

Large LCD display
Numeric keypad
On-screen menus in English, French, or Chinese
Real-time display of block temp, reference temp, cutout temp, stability, and ramp rate

Interfaces and Automation:

RS-232 serial interface
Compatible with Model 9930 Interface-it and xModel 9938 MET/TEMP II software
Supports fully automated calibration of RTDs, thermocouples, and thermistors

Pre-programmed functions (no PC required):

Up to 8 set points with ramp/soak
Automated “switch test” to identify thermal switch dead-band
Dedicated °C/°F switch button

Inserts and Portability

Choose from six standard inserts supporting both metric and imperial probe diameters
Units are compact and lightweight—easy to deploy in various environments

Model 9170 Summary

Temperature range down to –45 °C (in normal conditions)
Stability: ±0.005 °C
Immersion depth: 160 mm (6.3 in)
Axial uniformity: ±0.02 °C
Radial uniformity: ±0.01 °C

Specifications: Fluke Calibration 9173 Metrology Well

Specifications
Range (at 23°C ambient)	50°C to 700°C¹ (122°F to 1292°F)
Display accuracy	±0.2°C: 50°C to 425°C ±0.25°C: 425°C to 660°C
Stability	±0.005°C: 50°C to 100°C ±0.01°C: 100°C to 425°C ±0.03°C: 425°C to 700°C
Axial uniformity	±0.1°C: 50°C to 100°C ±0.25°C: 100°C to 425°C ±0.4°C: 425°C to 700°C
Radial uniformity	±0.01°C: 50°C to 100°C ±0.025°C: 100°C to 425°C ±0.04°C: 425°C to 700°C
Loading effect (with a 6.35 mm reference probe and three 6.35 mm probes)	±0.02°C at 425°C ±0.04°C at 700°C
Hysteresis	0.07°C
Well depth	203 mm (8 in)
Resolution	0.001°C
Display	LCD, °C or °F, user-selectable
Key pad	Ten key with decimal and ± button. Function keys, menu key, and °C / °F key.
Cooling time	235 min: 700°C to 50°C 153 min: 700°C to 100°C
Heating time	46 min: 50°C to 700°C
Size (H x W x D)	366 x 203 x 323 mm (14.4 x 8 x 12.7 in)
Weight	15 kg (33 lb)
Power	115 V AC (±10%), or 230 V AC (±10%), 50/60 Hz, 1025 W
Computer interface	RS-232 Interface
Traceable calibration (NIST)	Data at 100°C, 200°C, 350°C, 500°C, and 660°C
1. Calibrated to 660°C; reference thermometer recommended at higher temperatures.
Specifications	Built-in Reference Input
Temperature range	–200°C to 962°C (–328°F to 1764°F)
Resistance range	0 Ω to 400 Ω, auto-ranging
Characterizations	ITS-90 subranges 4, 6, 7, 8, 9, 10, and 11 Callendar-Van Dusen (CVD): R₀, a, b, d
Resistance accuracy	0 Ω to 20 Ω: 0.0005 W 20 Ω to 400 Ω: 25 ppm
Temperature accuracy (does not include probe uncertainty)	10 Ω PRTs: ±0.013°C at 0°C ±0.014°C at 155°C ±0.019°C at 425°C ±0.028°C at 700°C	25 Ω and 100 Ω PRTs: ±0.005°C at –100°C ±0.007°C at 0°C ±0.011°C at 155°C ±0.013°C at 225°C ±0.019°C at 425°C ±0.027°C at 661°C
Resistance resolution	0 Ω to 20 Ω: 0.0001 Ω 20 Ω to 400 Ω: 0.001 Ω
Measurement period	1 second
Probe connection	4-wire with shield, 5-pin DIN connector
Calibration	NVLAP accredited (built-in reference input only), NIST-traceable calibration provided