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A high-speed portable dew-point hygrometer, offering rapid spot-check measurements of dew point or moisture content in many applications, including compressed air, natural gas and high voltage switchgear quench gas. This lightweight, ATEX, IECEx, FM, CSA, GOST and INMETRO certified product allows more measurements per working hour than any other comparable product. A hard-wearing but ergonomic case and an easy-to-use interface allows comfortable operation in the toughest industrial environments.  



Technical Specification


MDM300 Intrinsically Safe


Measurement Technology

Michell ceramic sensor


±1°C from -60 to +20°C (±1.8°F from -76 to +68°F) dew point
±2°C from -100 to -60°C (±3.6°F from -148 to -76°F) dew point
±0.2°C temperature (0.36°F)

Calibrated Range

Spot Checks: -70 to +20°C (-94 to +68°F) dew point 
Online Analysis: -100 to -70°C (-148 to -94°F) dew point

Uncalibrated Readings From

+20 to +30°C (+68 to +86°F) dew point

Measurement Units

°C, °F, K dew point & gas temperature ppmV,
ppmW for air, N2, H2, CO2, SF6
%RH, g/m3, g/kg
Option: active pressure (bara/g, psig, MPa, KPa)

°C, °F, K dew point & gas temperature
ppmw & g/kg for air, N2, H2, CO2, SF6
ppmv, lb/MMscf & g/m3 for natural gas
ppmv, g/m3 & %RH

Resolution (Display)

0.1 for all dew-point derived units and autoranging where appropriate

Resolution (Measurement)

Better than 0.1°C (0.18°F) dew point

Typical Response Speed

T95 in ≤15 minutes to -60°C (-76°F) dew point

T95 in ≤30 minutes to -60°C (-76°F) dew point

Measurement System Repeatability

Better than 0.1°C (0.18°F) dew point

Measurement System Hysteresis

±0.05°C (0.09°F) dew point

Electrical Input/Output

Auxiliary Inputs

4-20 mA loop-powered external input selectable as either dew point, temperature or pressure

Connection to Michell Easidew TX I.S. or Easidew PRO I.S. via Remote Sensor Interface

Battery Type

NiMH 4.8V

Battery Operating Life

Up to 48 hours of typical usage between charges

Up to 24 hours of typical usage between charges

Battery Charger

Intelligent charger (supplied)

Intelligent charger (not certified for hazardous area use)

Operating Conditions

Operating Pressure

35 MPa (350 barg / 5076 psig) max (Please consult your Michell Sales Engineer for advice on operating at pressure exceeding 15 MPa (150 barg / 2175 psig)

Operating Environment

Outdoors 0 to +100% RH condensing

Operating Temperature

-20 to +50°C (-4 to +122°F)

Storage/Transport Temperature

-40 to +70°C (-40 to +158°F)

Mechanical Specification


Blue LCD graphical display

Enclosure Type

Steel fiber-loaded high-impact polyamide 6

IP/NEMA Rating


Gas Connections

1/8” NPT female (other options available)

Flow Across Sensor

0.2 to 1.2 Nl/min (0.42 to 2.54 scfh)

0.2 to 0.5 Nl/min (0.42 to 1.05 scfh)

Gas Wetted Materials

AISI 316L stainless steel

AISI 316L stainless steel, PTFE Seal, Borosilicate glass, ceramic

Outline Dimensions

218 x 170 x 90mm (8.6 x 6.7 x 3.5") (d x w x h)


1.35kg (2.98lbs)

1.5kg (3.31lbs)


Data Logging

8 megabytes; Log interval: 5 to 60 sec; Logs per log file: Up to 10,000


(Wireless) BluetoothTM range up to 5m (16.4’) (version 2.0)

User Interface Languages

English, French, German, Italian, Portuguese, Spanish

Certification Codes


ATEX & IECEx – EX Group II Cat 1G Ex ia IIC T4 Ga -20°C to 60°C
CSA/FM – NEC 500 Class1 Div 1 Groups A,B,C,D T4
INMETRO: Ex ia IIC T4 Ga (-20°C to +50°C)


. Repeatedly fast measurements at low pressure in less than 15 minutes for T95 down to -60°C dew point . (-76°F   dew point)
. Higher pressure measurements possible – up to 35 MPa (350 barg / 5076 psig)
. Long battery life: up to 48 hours of typical use between charges
. Intuitive application kits allow quick and straightforward connection to your sample point
. Durable, yet easy to handle and operate: designed for use in industrial environments 
. 4-20mA external device input for transmitter calibration and validation 
. Lightweight: less than 1.5kg (3.31 lbs) 
. 13 point traceable calibration certificate 

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