Zeal Wet and Dry Bulb Hygrometer
A Zeal Wet & Dry Bulb Hygrometer is an analog psychrometer instrument designed to measure relative humidity (RH) by comparing two temperature readings:
- The dry-bulb thermometer gives the ambient air temperature.
- The wet-bulb thermometer has a wick or cloth soaked in water; evaporation cools it, so its reading is lower than or equal to the dry-bulb reading.
From the difference between these two readings, one can compute relative humidity (or read it using psychrometric tables). The Zeal version is a traditional, non-electronic, pinless device, often with a molded plastic case, protective lid, and included tables for humidity conversion. Zeal offers models such as the P2505 “Masons Pattern Hygrometer,” housed in a yellow case with spare wick and instructions. The device is also described as “Mason’s type” in listings.
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Specification |
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Temperature range |
About –8 °C to +50 °C (20 °F to 120 °F) in many listings. |
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Scale/Units |
Dual scale: Celsius (°C) and Fahrenheit (°F) |
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Analog/Manual |
No electronics or batteries; readings are manual using mercury or spirit thermometers. |
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Case/Protection |
Molded plastic case (often yellow) with lid and bulb protection, wall or mounting provision. |
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Bulbs and Wick |
Two thermometers mounted side by side, with a cotton or cloth wick for the wet bulb and a reservoir for water |
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Supplied accessories |
Hygrometric (psychrometric) tables to convert temperature difference to relative humidity, spare wick, instructions. |
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Mounting / Use |
Often wall-mountable or set up in a place with free air movement for proper readings. Some are “pinless” designs (i.e. without an exposed pin or needle). |
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Accuracy / Tolerance |
Typical analog psychrometers have modest accuracy; user care (ventilation, wick condition, calibration) affects reliability. Some listings claim “±2” (units likely °C) tolerance. |
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Wight / Size |
Lightweight—some versions weigh ~150 g. Industry Buying One listing gives the Zeal unit’s dimensions ~10 cm × 3 cm, weight ~499 g (though that may be with packaging) |
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No power requirement |
Operates without batteries or electronics, relying purely on the physical principle of evaporation. |
