Durable Temperature and Humidity Sensor

The durable temperature and humidity sensor (Model number HTY1000, HTY1010) is a highly precise and reliable sensor using the resistance temperature detector (Pt100, JIS C1604 class A) for the temperature sensor and the macromolecule capacitance type humidity sensor, FP4™ developed by Azbil Corporation.
JIS: Japanese Industrial Standards

Basic operation

There are two sensors, sensor 1 and sensor 2.
When one of the two sensors is being heated, measurement is carried out by the other one and the results can be output.
Each sensor has two measuring modes, measuring and non-measuring mode.
When one sensor is in the measuring mode, its measured value will be displayed on the LCD and be output as an analog value.
The other one is in non-measuring mode.

Correction between two sensors

If a measurement, temperature, or humidity error occurs between the two sensor, the sensor 2 is tuned to be the same value with the sensor 1 by adjusting the start time of heating.

Environment-resistant function

This temperature/humidity sensor, FP4 developed by Azbil, consists of two elements: Temperature sensing element (resistance temperature detector Pt100) and Macromolecule capacitance type humidity sensing element.
The resistance temperature sensor (Pt100) is also used for heating the humidity sensing element in order to recover or detect each deterioration mode.

< Drift recovery function >
The temperature/humidity sensing element, FP4, vaporizes the residual chemicals in macromolecules by heating process in order to recover the drifted performance to its initial state.
The applicable chemicals for this function and resistances to them are described below.

  • Continuous exposure concentrations
    When 10 minutes heating process is carried out every 24 hours, the concentration and period in which the drifted value is recovered within ±2 % RH.

Chemical resistance of drift recovery function

Chemical Specification
Organic solvent Ethanol 250 ppm Exposed for 3 years 10 minutes heating every 24 hours
Organic solvent Acetone 100 ppm Exposed for 3 years 10 minutes heating every 24 hours
Organic solvent Methyl ethyl ketone 100 ppm Exposed for 3 years 10 minutes heating every 24 hours
Organic solvent Ethyl lactate 50 ppm Exposed for 3 years 10 minutes heating every 24 hours
Organic solvent NMP (N-methyl-2-pyrrolidone) 200 ppm Exposed for 3 years 10 minutes heating every 24 hours
  • Allowable concentrations
    After 24 hours exposure, the concentrations and heating period in which the drifted measured value is recovered within ±1 % RH.

Chemical resistance of drift recovery function

Chemical Specification
Organic solvent Ethanol 1000 ppm Exposed for 24 hours 15 minutes heating
Organic solvent Acetone 750 ppm Exposed for 24 hours 20 minutes heating
Organic solvent Methyl ethyl ketone 300 ppm Exposed for 24 hours 15 minutes heating
Organic solvent Ethyl lactate 50 ppm Exposed for 24 hours 10 minutes heating
Organic solvent NMP (N-methyl-2-pyrrolidone) 200 ppm Exposed for 24 hours 10 minutes heating
  • Reference
    Chemical resistances not related with heating recovery function is described below.
Chemical Specification
Disinfectant Formalin 300 ppm Exposed for 24 hours ±5 % RH
Inorganic compound Ammonia 10 ppm Exposed for 24 hours ±3 % RH

< Drift detection function >
Since the humidity sensor's element needs to be exposed to the measurement atmosphere, it cannot be separated from the external environment.
Therefore, a certain amount of drift cannot be avoided.
The main environment and deterioration modes that cause a drift are described below.

Main environment and deterioration modes

Operation environment Cause of drift Deterioration modes Detection function
Manufactures of semiconductor, pharmacy, etc. Organic solvents evaporated from the production material, adhesives, ink, etc. Since the organic solvents infiltrate into the macromolecule and its conductivity changes, the measurement value will drift.
Especially in a lower humidity environment (less than 30 % RH) , the drift tends to large.
According to the operating environment, it may deteriorate in a short period.
The drift recovery function is effective.
Drift detection 1
Animal breeding facilities, hospitals, etc (open air, hot spring, etc.) Salts contained in disinfectants, acids, sulfurous acid gas in the air When the substance, adhering on the surface or nearby of element, absorbs moisture, the measurement value will drift.
Especially in a higher temperature environment, the drift tends to large.
It will take time to deteriorate.
The drift will be recovered temporarily by the drift recovery function.
Drift detection 2

(Note) The drift may be recovered by cleaning the element.
For details, refer to (the document.)

  • Drift detection 1
    If organic solvents cannot be removed by the heating operation, the measurement value may drift.
    Although the relative humidity of the humidity element while heating is almost 0 %, if an organic solvent remains in a humidity element, it will become a high value. The measured humidity while heating is compared with the initial value (shipped from factory) to detect the drift.

(Note) If the dew point temperature of ambient during heating operation is 30 °C Td or more, the drift detection 1 cannot be detected.

  • Drift detection 2
    When the deliquescent (hygroscopic) substance adheres on the surface or nearby of element, the measured humidity may drift higher.
    Although the deliquescent substance will not be removed by heating, the drift will be recovered temporarily since the moisture is evaporated.
    Therefore, the humidity measurement value of an element that was heated is compared with the value of another element to detect the drift.

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