Michell Instruments S4000 Specifications

Chilled Mirror Instruments

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S4000 TRS

Precision Dew-Point Hygrometer

A precision laboratory dew-point hygrometer with the ultimate accuracy, reliability and long
term performance for humidity measurement and calibration.

Highlights

• 0.1°Cdp accuracy (0.18°Fdp)

• Measurement range: -100 to +20°Cdp

(-148 to +68°Fdp)

• Precision 100 Ω 4-wire platinum resistance
thermometer

• Dual optics detection system

• Available with VCR couplings for optimum trace

moisture sampling

• Dual multi-function LED display with unit
indicator

Applications

• Standards Laboratory reference instrument

• Research and development

• Battery manufacture

• Industrial gases

Chilled Mirror Instruments

S4000 TRS
Precision Dew-Point
Hygrometer

The Laboratory Standard

The S4000 TRS offers unmatched accuracy and reliability in
dew-point measurement and calibration. The powerful three­stage Peltier thermoelectric heat pump, coupled with integrated
auxiliary refrigerant cooling, gives an effective measurement
range down to -100°C (-148°F) dew point.

Dual Optics for Supreme Sensitivity

At low frost points the rate of formation of frost on the mirror
surface is extremely slow. As a result other chilled mirror dew­point meters may give reduced accuracy, poor control stability
and extremely long response times at low moisture levels. The
S4000 TRS is unique in that it utilizes a dual optics detection
system. This greatly increases the sensitivity of the optical loop.
Response, stability and sensitivity are improved by orders of
magnitude at low frost points.

Calibration Integrity

The S4000 TRS is unique amongst dew-point hygrometers. It
is the only instrument that is delivered, as standard, with a full
UKAS certificate providing official traceability to the UK National
Standard. UKAS is the United Kingdom member of European
Co-operation on Accreditation (EA), the International Laboratory
Accreditation Cooperation (ILAC) and the International
Accreditation Forum (IAF). As an additional benefit, the S4000
TRS has a direct traceability path to the NIST (Washington DC,
USA) National Humidity Standard.

No other hygrometer provides such comprehensive traceability
to a worldwide network of standards organizations. The S4000
TRS is used by many of these organisations as part of their own
humidity referencing systems.

Contamination Compensation

Any optical system carries a risk of contamination. The
S4000 TRS automatically compensates for any such build­up with its ABC (Automatic Balance Compensation) System.
ABC ensures continuous optimum operation of the sensor by
periodically driving off condensation to allow the optical loop
to be rebalanced. When the contamination level is too high a
visible alarm is generated. The sensor optical system may be
cleaned with distilled water or a suitable high purity solvent
such as acetone. ABC cycle time, duration and recovery time
can all be adjusted according to the type of application to
minimize the effect of contamination risk. The S4000 TRS also
features a sophisticated data hold system, which maintains the
instrument’s signal outputs during an ABC cycle, allowing the
S4000 TRS to be used for process control applications.

Unbeatable Measurement Capability

The S4000 TRS uses a highly accurate 4-wire PT100
temperature sensor and has a proven measurement capability of
better than ±0.1°C (±32.18°F) dew point.

Visual Verification

Every S4000 TRS is delivered complete with an M4K Viewing
Microscope. Fitting neatly into the sensor viewing port, this
microscope allows the user to confirm the presence of water or
ice on the mirror surface.

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Chilled Mirror Instruments

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3

Technology:
Chilled Mirror

Michell’s chilled mirror dew-point hygrometers are precision
instruments for critical measurement and control applications.
Chilled mirror sensors measure a primary characteristic of
moisture – the temperature at which condensation forms on a
surface. This means that chilled mirror instruments:

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• have no drift: the temperature at which condensation forms
is measured directly so there are no calculated variables that
could shift over time

• are inherently repeatable, giving reliable results every time

The chilled mirror sensor consists of a temperature controlled
mirror and an advanced optical detection system.

A beam of light from an LED (1) is focused on the mirror surface
(2) with a fixed intensity. As the mirror is cooled, less light is
reflected due to the scattering effect of the condensate formed
on the mirror surface. The levels of reflected and scattered light
are measured by two photo-detectors (3 & 4) and compared
against a third reference detector (5) measuring the intensity of
light from the LED.

The signals from this optics system are used to precisely
control the drive to a solid state thermoelectric cooler (TEC)
(6), which heats or cools the mirror surface. The mirror
surface is then controlled in an equilibrium state whereby
evaporation and condensation are occurring at the same rate.
In this condition the temperature of the mirror, measured by a
platinum resistance thermometer (7), is equal to the dewpoint
temperature of the gas.

An auxiliary cooling system (8) is used to remove heat from the
‘hot’ side of the TEC. This supplements the depression
capabilities of the heat pump, and enables measurement of very
low dew points.

Our chilled mirror instruments prove their reliabilty on a daily
basis in our production processes and service centres, as well as
in our UKAS-accredited calibration laboratory.

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4

2

6

7

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Chilled Mirror Instruments

Performance

Measurement technology Chilled Mirror

Measurement range TRS: -100 to +20°Cdp (-148 to +68°Fdp)

Measurement accuracy ±0.1°Cdp (±0.18°Fdp)

±0.1°C temperature (±0.18°Fdp)

Measurement units °Cdp, °Fdp; °C, °F temperature;

% RH, ppmV, ppmW, g/m3, g/kg,
ppmW for SF

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Response speed 0.5°C/sec (0.9°F/sec) + settling time

(dew point dependent)

Sensitivity 0.01°C (0.02°F)

Repeatability Better than 0.1°C (0.18°F)

Resolution 0.01 (0.1 for % RH)

Dew-Point Sensor

Mirror Gold plated copper

Temperature 4 wire Pt100, 1/10 DIN class B
measurement

Sample flow rate 0.1 to 0.7 Nl/min (recommended)

(0.21 to 1.48 scfh)

Integrated flowmeter 0 to 1 Nl/min (0 to 2.12 scfh)

Sensor pressure Atmospheric

Auxiliary cooling Internal refrigeration

Remote PRT

Temperature 4 wire Pt100, 1/10 DIN class B
measurement

Monitor

Resolution 0.01°C (0.02°F)

Dual optics detection Wide band red LED with dual photo sensors, all

system insulated

Outputs

Analog 2 channels

10 mV/°Cdp, 4-20 mA

Digital RS232

Logic Data hold, ABC Logic status, optics alarm

Auxiliary input 4-20 mA input for automatic
pressure transducer compensation 0-0.34 MPa (0-50 psia) (optional)

Operating temperature 0 to +40°C (32 to 104°F)

Dimensions 560W x 600D x 860mm - mini rack

(22.05 x 23.62 x 33.86 inches)

Weight 85.0kg (187.39lbs)

Power supply

Monitor 90 to 265 V AC; 50-60 Hz

Sensor 100 to 115 or 220 to 240 V AC 50-60 Hz

Technical Specifications

Dimensions

© 2012 Michell Instruments

Michell Instruments Ltd, Rotronic Instruments Corp. 135 Engineers Road, Suite 150, Hauppauge
NY 11788. Tel: [phone], Email: [e-mail], Web:

Michell Instruments adopts a continuous development programme which sometimes necessitates specification changes without notice.
Issue no: S4000 TRS_97146_V4.1_US_0718

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