Fluke 9170 Specifications

9170 Series

Metrology Well Calibrators

• Best-performing industrial heat sources
(accuracy, stability, uniformity) in the
world

• Immersion depth to 203 mm (8 in)

• Optional ITS-90 reference input reads
PRTs to ±0.006 °C

• Temperature range from –45 °C to 700 °C

In short, there are six critical
components of performance in
an industrial heat source (which
the European metrology com­munity explains, for example, in
the document EA-10/13): cali­brated display accuracy, stability,
axial (vertical) uniformity, radial
(well-to-well) uniformity, impact
from loading, and hysteresis. We
added a seventh in the form of a
legitimate reference thermometer
input and created an entirely new
product category: Metrology Wells.
(By the way, Metrology Wells are
the only products on the market
supported by published specifica­tions addressing every perfor­mance category in the EA-10/13.
Our specs aren’t just hopes or
guidelines. They apply to every
Metrology Well we sell.)

Technical Data

Every once in a while, a new
product comes around that
changes the rules. It happened
when we introduced handheld
dry-wells. It happened when
we introduced Micro-Baths. Now
we’ve combined bath-level per­formance with dry-well func­tionality and legitimate reference
thermometry to create Metrology
Wells.
With groundbreaking new pro­prietary electronics from Fluke

Calibration (patents pending),
Metrology Wells let you bring lab­quality performance into whatever
field environment you might work
in. New analog and digital con­trol techniques provide stability
as good as ±0.005 °C. And with
dual-zone control, axial (or “ver­tical”) uniformity is as good as
±0.02 °C over a 60 mm (2.36 in)
zone. (That’s 60 mm!) Such per­formance doesn’t exist anywhere
else outside of fluid baths.

Display accuracy

Dry-wells are typically calibrated
by inserting a calibrated PRT
into one of the wells and mak­ing adjustments to the calibra­tor’s internal control sensor based
on the readings from the PRT.
This has limited value because
the unique characteristics of the
reference PRT, which essentially
become “calibrated into” the cali­brator, are often quite different
from the thermometers tested by
the calibrator. This is complicated
by the presence of significant
thermal gradients in the block

Built-In Reference Thermometry!

Fluke Calibrationhas been making the
world’s best thermometer readout devices
for quite some time. Our Super-Thermom­eter, Black Stack, and Tweener thermom­eters are well-known everywhere. Now
we’re making our proprietary Tweener
measurement circuitry available directly
in a heat source — our new Metrology
Wells.
This optionally built-in input accepts
100-, 25-, and 10-ohm PRTs. It reads
thermometer probes accurately from
±0.006 °C at 0 °C to ±0.027 °C at 661 °C,
not including errors from the probe. It is
compatible with every PRT sold by Fluke
Calibration and connects to Metrology
Wells via a 5-pin DIN connector.

and inadequate sensor immersion
into blocks that are simply too
short.
Metrology Wells are different.
Temperature gradients, loading
effects, and hysteresis have been
minimized to make the calibra­tion of the display much more
meaningful. We use only trace­able, accredited PRTs to calibrate
Metrology Wells and our proprie­tary electronics consistently dem­onstrate repeatable accuracy more
than ten times better than our
specs, which range from ±0.1 °C
at the most commonly used tem­peratures to ±0.25 °C at 661 °C.
For even better accuracy, Metrol­ogy Wells may be ordered with
built-in electronics for reading
external PRTs with ITS-90 char­acterizations. (See sidebar, Built-in
Reference Thermometry, above.)

Stability

Heat sources from Fluke Calibra­tion have long been known as
the most stable heat sources in
the world. It only gets better with
Metrology Wells. Both low-tem­perature units (Models 9170 and

9171) are stable to ±0.005 °C over
their full range. Even the 700 °C
unit (Model 9173) achieves sta­bility of ±0.03 °C. Better stability
can only be found in fluid baths

Two things dramatically differentiate
the Tweener circuit from the measure­ment electronics built into many dry­wells. First, it accepts unique ITS-90
characterization coefficients from refer­ence thermometers, which allow you to
take full advantage of the accuracies of
those thermometers. Second, it comes
with a traceable, accredited calibra­tion, providing you full confidence in the
integrity of its measurements.
Nothing beats a Fluke Calibration
Metrology Well for industrial thermal per­formance. And nothing beats a Tweener
measurement for built-in reference ther­mometry.

and primary fixed-point devices.
The “off-the-shelf controllers”
used by most dry-well manufac­turers simply can’t provide this
level of performance.

Axial uniformity

The EA-10/13 document suggests
that dry-wells should include a
zone of maximum temperature
homogeneity, which extends for
40 mm (1.54 in), usually at the
bottom of a well. Metrology Wells,
however, combine our unique
electronics with dual-zone con­trol and more well depth than
is found in dry-wells to provide
homogeneous zones over 60 mm
(2.36 in). Vertical gradients in
these zones range from ±0.02 °C
at 0 °C to ±0.4 °C at 700 °C.
What’s more, Metrology Wells
actually have these specifications
published for each unit, and we
stand by them.

Radial uniformity

Radial uniformity is the differ­ence in temperature between
one well and another well. For
poorly designed heat sources, or
when large-diameter probes are
used, these differences can be
very large. For Metrology Wells,
we define our specification as the
largest temperature difference

between the vertically homo­geneous zones of any two wells
that are each 6.4 mm (0.25 in)
in diameter or smaller. The cold
units (9170 and 9171) provide
radial uniformity of ±0.01 °C and
the hot units (9172 and 9173)
range from ±0.01 °C to ±0.04 °C
(at 700 °C).

Loading

Loading is defined as the change
in temperature sensed by a refer­ence thermometer inserted into
the bottom of a well after the rest
of the wells are filled with ther­mometers, too.
For Metrology Wells, loading
effects are minimized for the
same reasons that axial gradients
are minimized. We use deeper
wells than found in dry-wells.
And we utilize proprietary dual­zone controls. Loading effects are
as minimal as ±0.005 °C in the
cold units.

Hysteresis

Thermal hysteresis exists far more
in internal control sensors than
in good-quality reference PRTs.
It is evidenced by the difference
in two external measurements
of the same set-point tempera­ture when that temperature is
approached from two different
directions (hotter or colder) and
is usually largest at the midpoint
of a heat source’s temperature
range. It exists because control
sensors are typically designed for
ruggedness and do not have the
“strain free” design characteristics
of SPRTs, or even most PRTs. For
Metrology Wells, hysteresis effects
range from 0.025 °C to 0.07 °C.

Immersion depth

Immersion depth matters. Not
only does it help minimize axial
gradient and loading effects, it
helps address the unique immer­sion characteristics of each
thermometer tested in the heat
source. Those characteristics
include the location and size

2 Fluke Calibration, Metrology Well Calibrators