Michell Instruments WM291 Specifications

Humidity and Dew-Point Instruments

Precision Manufacturing

WM291

Digital Relative Humidity & Temperature Transmitter, Wall Mount

Technical Speciﬁ cations

Performance

Measurement range (RH) 0–100% RH Measurement range (T) -30 to +70°C (-22 to +158°F)

HYGROSMART ®

INTERCHANGEABLE MODULE

The WM291 relative humidity transmitter includes the interchangeable Hygrosmart module. The interchangeable module lets you recalibrate the transmitter simply by replacing the sensor head with the Hygrosmart module. As a result, maintenance costs are greatly reduced and down-time is minimized.

Highlights

Three outputs•

Analog and digital output standard•

Based on the interchangeable Hygrosmart module•

Analog output signals selectable through software•

Metric or US measurement units selectable through • software

Available with calculated absolute humidity, dew-point, • frost point, mixing ratio or speciﬁ c enthalpy output

Accuracy at 23°C (73°F) Humidity

Accuracy at 23°C (73°F) Temperature

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

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 IP65 (NEMA 4 level) Material

Housing Probe

Dimensions

Housing Probe

Weight 450g (15.87oz) Electrical connections Screw terminals Display resolution LCD, 2 lines x 16 characters

<±2% RH (5-95% RH)

±0.4°C (±0.72°F)

change)

0–20 mA, 4–20 mA, RS485

-30 to +85°C (-22 to +185°F)

-20 to +70°C (-4 to +158°F)

-30 to +70°C (-22 to +158°F)

Aluminum die casting Delrin

120 x 120 x 49.5mm (4.72 x 4.72 x 1.94”) L=100mm, ø19mm (L=3.93”, ø0.74”)

Dimensions

Issue No: WM291_97186_V2_UK_1110

Accessories and Spare Parts

RS422/485 to PC (RS232) converter 330185 USB cable/software for conﬁ guration F035263 SS sintered ﬁ lter H2 SS sintered ﬁ lter with teﬂ on coating J2 Delrin cap slotted with SS mesh ﬁ lter K7 Delrin cap slotted with PTFE ﬁ lter, white Z7 Hygrosmart with Pt100 output (RH = 0-1 V) I7-0-00-1

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

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

WM291

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 Output Channel 1 Temperature + 12 Not connected

6 Output Channel 1 Ground 13 Output Channel 3 (optional)

7 Output Channel 2 RH + 14 Output Channel 3 Ground (optional)

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}+{Feature E}+{Feature F}

Precision Manufacturing

Order example:

Digital RH and temperature transmitter WM291 for wall-mounting, 4-20 mA output, dp display -40 to +100ºC, Delrin cap slotted, with stainless steel mesh ﬁ lter, temp range -30 to +70ºC (-22 to +158ºF)

Base Model {Feature A}

Digital RH and temperature transmitter WM291

Signal Output {Feature B}

4–20 mA A

0–10 V B

0–5 V C

0–1 V D

0–20 mA E

3rd Output {Feature C}

Dew point: -40 to +100ºC 0

Mixing ratio: 0-500 gr/Kg 1

Absolute Humidity: 0 - 600 g/m

Speciﬁ c enthalpy: -40 to 1500 KJ/Kg 3

Frost point: -50 to +10ºC 4

WM291+A+0+K7+N030+P070

WM291 A 0 K7 N030 P070

Temp High {Feature F}

+20°C (+68°F) P020

+30°C (+86°F)) P030

+50°C (+122°F) P050

+70°C (+158°F) P070

Other output scaling available on request XXXX

Temp Low {Feature E}

0°C (+32°F) 0000

-20°C (-4°F) N020

-30°C (-22°F) N030

Filter {Feature D}

SS sintered ﬁ lter H2

SS sintered ﬁ lter with teﬂ on coating J2

Delrin cap slotted, with SS mesh ﬁ lter K7

Delrin cap slotted, with PTFE ﬁ lter, white Z7