Product guide
43
Humidity and Dew-Point Instruments
Please note: Michell Instruments adopts a continuous development program which sometimes
necessitates specifi cation changes without notice. Please contact us for latest version.
www.michell.com
Precision Manufacturing
WM291
Digital Relative Humidity & Temperature Transmitter, Wall Mount
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
Technical Specifi cations
Performance
Measurement range (RH) 0–100% RH
Measurement range (T) -30 to +70°C (-22 to +158°F)
Accuracy at 23°C (73°F)
Humidity
<±2% RH (5-95% RH)
Accuracy at 23°C (73°F)
Temperature
±0.4°C (±0.72°F)
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
0–20 mA, 4–20 mA, RS485
Supply voltage 15 - 27 V AC / 18 - 38 V DC
Load resistance Current output: R 500
Power consumption 1.7 W
Operating conditions
Operating temperature
Probe
Housing
Storage
-30 to +85°C (-22 to +185°F)
-20 to +70°C (-4 to +158°F)
-30 to +70°C (-22 to +158°F)
Mechanical specifi cation
Ingress protection IP65 (NEMA 4 level)
Material
Housing
Probe
Aluminum die casting
Delrin
Dimensions
Housing
Probe
120 x 120 x 49.5mm (4.72 x 4.72 x 1.94”)
L=100mm, ø19mm (L=3.93”, ø0.74”)
Weight 450g (15.87oz)
Electrical connections Screw terminals
Display resolution LCD, 2 lines x 16 characters
INTERCHANGEABLE
MODULE
HYGROSMART ®
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
HKC
Issue No: WM291_97186_V2_UK_1110
Dimensions