EMD Relative Humidity Sensor

EMD-2000 Sensor

First, there was the EMD-2000 sensor, known for its tight accuracy and strong resistance to chemicals. The EMD-2000 which offers not only high accuracy but also improved hysteresis and a compact size. Both sensors are bulk polymer RH sensors that change resistance as the relative humidity changes. Now, the EMD-4000 is capable of withstanding environments where organic vapors are present. It recovers from condensing environments and may be used at temperatures up to 185°F (85°C)

EMD Relative Humidity Sensors are ideal for humidity measurement applications that require a high degree of accuracy without calibration. The EMD-2000 sensor includes an HDPE filter cover that protects the sensor during handling and helps keep contaminants from affecting performance.

The EMD-4000 is capable of insitu measurement of soluble water in organic liquids such as transformer oil, gasoline, toluene, acetone, and other compounds of varying hydrogen bond strengths. The EMD-4000 is highly repeatable and interchangeable.

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EMD Sensor Specifications


  • < ± 1% Hysteresis
  • Excellent Long Term Stability (< 1% RH/Year)
  • Available Accuracies of ± 1, 2, 3, 5% RH
  • Exceptional Chemical Resistance
  • Compact Package




%RH Range at 77°F (25°C) 20% to 95%
Operating Temperature 41°F to 140°F (5°C to 60°C)
Storage 0% to 95% RH, -40°F to 185°F (-40°C to 85°C)
Accuracy • ±5% RH standard
• ±3% RH available
Repeatability ±0.5% RH
Impedance 72K S at 77°F (25°C), 50% RH with 1 VAC at 1 KHz
Response Time  
Hysteresis <1% RH at 77°F (25°C) for step change from 30% to 98%
RH then back to 30% RH
Temperature Dependence 0.5% RH/°F (°C, average)
Long Term Drift 0.1% RH/year typical in clean, chemical free air

0.2 in (5.1 mm) wide x 0.4 in (10.2 mm) high x 0.02 in (0.51 mm) thick

Leads: 0.4 in (10.2 mm) long x 0.15 in (3.81 mm) wide x
0.01 in (0.25 mm) thick on 0.1 in (2.54 mm) centers

Exposure to Saturated Chemical Vapors • Toluene, 25,200 ppm/3 days: <2% RH drift
• Hexane, 152,000 ppm/3 days: <2% RH drift
• Methanol, 127,000 ppm/3 days: <5% RH drift
Transformer Oil; 60K S at 30 ppm at 77°F (25°C) • 3 months at 77°F (25°C): <5% drift, 2% RH typical
• 1 month at 185°F (85°C): <5% drift, 2% RH typical
Water Vapor Saturation 100% RH/77°F (25°C)/1000 hours storage; <3% RH drift typical; 1/16 in (1.59 mm) water droplet covering entire sensor surface for 10 minutes followed by drying via air ventilation; <5% drift
Caution -DC current should never be applied to the EMD-4000 humidity sensor. Application of direct current will polarize the sensor and cause an irreversible shift. Only a symmetrical AC excitation current should be applied. GE recommends that application of a low level AC excitation (1 VAC, 1 KHz typical) to minimize self-heating effects.


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