Michell Instruments WR285 Specifications

Humidity and Dew-Point Instruments

Precision Manufacturing

WR285

Digital Relative Humidity Transmitter - Remote Probe for Pressurized
Applications up to 30 bar (400 psi)

Technical Specifi cations

Performance

Measurement range (RH) 0–100% RH

HYGROSMART ®

INTERCHANGEABLE
PROBE

The WR285 relative humidity sensor uses the Hygrosmart
module, integrated in the interchangeable probe. This device
can be used in high-temperature applications due to the
remote measurement element and its small overall size. The
interchangeable probe allows for simple recalibration and
lower maintenance costs.

Highlights

Up to 30 bar (400 psi) pressure•

Analog and digital output standard•

Interchangeable probe•

Analog output signals selectable through software•

Metric or US measurement units selectable through •
software

Can withstand temperatures up to 120• °C (248°F)

Accuracy at 25°C (77°F)
Humidity

Stability – RH Sensor ±1% RH/year
Response time – RH Sensor <10 sec typical (for 90% of the step change)

Electrical output/input

Output signal 0–1, 0–5, 0–10 V

Supply voltage 15 - 27 V AC / 18 - 38 V DC
Load resistance Current output: R ≤ 500 Ω
Power consumption 1.7 W

Operating conditions

Operating temperature

Probe
Housing
Storage

Mechanical specifi cation

Ingress protection IP67
Material

Housing
Probe

Dimensions

Housing
Probe

Weight 450g (15.87oz)
Electrical connections Screw terminals

<±2% RH (5–95% RH)

0–20 mA, 4–20 mA, RS485

-30 to +120°C (-22 to +248°F)

-30 to +70°C (-22 to +158°F)

-40 to +70°C (-40 to +158°F)

Aluminum die casting
Stainless steel

120 x 120 x 51mm (4.72 x 4.72 x 2.00”)
L=148mm, ø18mm (L=5.82”, ø0.70”)

Dimensions

Issue No: WR285_97193_V2_UK_1110

Accessories and Spare Parts

RS422/485 to PC (RS232) converter 330185
USB cable/software for confi guration F035263
SS interchangeable probe with 2m (6.56') cable USTE015
SS cap slotted with mesh fi lter K1
SS cap slotted with PTFE fi lter Z1

You can check your hygrometer with the Control Kit HKC
which is based on the principle of non-saturated salt
solutions. Refer to technical data sheet CONTROL KIT

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Please note: Michell Instruments adopts a continuous development program which sometimes
necessitates specifi cation changes without notice. Please contact us for latest version.

HKC

www.michell.com

Humidity and Dew-Point Instruments

WR285

Electrical Connections

Pin Pin

1 Power Supply V + 8 Output Channel 2 Ground

2 Power Supply V - 9 RS485 Data +

3 Output RS485 Ground 10 RS485 Data -

4 Ground 11 Not connected

5 Not connected 12 Not connected

6 Not connected 13 Output Channel 3 (not connected)

7 Output Channel 2 RH + 14 Output Channel 3 Ground (not connected)

Do not connect pin 2 (V -) to pin 4 (Ground)

Ordering Codes

To construct the order code, select the relevant feature from the tables below, starting with the base model, which is {Feature A} and then add on options to create a
string: {Feature A}+{Feature B}+{Feature C}+{Feature D}

Precision Manufacturing

Order example:

Digital RH transmitter WR285, 4-20 mA output, stainless steel probe with 2m (6.56’) cable, stainless steel cap with mesh fi lter

Base Model {Feature A}

Digital RH transmitter WR285

Signal Output {Feature B}

4–20 mA A

0–10 V B

0–5 V C

0–1 V D

0–20 mA E

WR285+A+15+K1

WR285 A 15 K1

Filter {Feature D}

SS cap slotted with mesh fi lter K1

SS cap slotted with PTFE fi lter Z1

Probe Type {Feature C}

SS interchangeable probe with 2m (6.56’) cable 15

© Michell Instruments 2009-2011

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