Explanation:
Hygrometer:
- A hygrometer is an instrument used to measure the amount of water vapour in the air (humidity), in soil, or in confined spaces.
- Humidity measurement instruments usually rely on measurements of some other quantities such as -
- Temperature, pressure, mass, a mechanical or electrical change in a substance as moisture is absorbed.
Additional Information
Hydrometer:
- A hydrometer is an instrument used for measuring the relative density of liquids based on the concept of buoyancy.
- They are typically calibrated and graduated with one or more scales such as specific gravity.
- Hydrometers can be divided into two general classes -
- liquids heavier than water
- liquids lighter than water
A photometer is used to measure the intensity of light produced by an unknown source in terms of a standard source.
- It is an instrument that measures the strength of electromagnetic radiation in the range from ultraviolet to infrared and including the visible spectrum.
- Most photometers convert light into an electric current using a photoresistor, photodiode, or photomultiplier.
- Photometers are used to determine the correct exposure in photography.
- Photometers measure Illuminance, Irradiance, Light absorption, Scattering of light, Reflection of light, Fluorescence, Phosphorescence and Luminescence.
| Instrument | Use |
|---|---|
| Ammeter | Measures the strength of the electric current. |
| Anemometer | Measures wind speed. |
| Barometer | Measures atmospheric pressure. |
| Bolometer | Measures heat radiations. |
| Crescograph | Measures growth in plants. |
| Calorimeter | Measures heat in chemical reactions. |
| Hydrometer | Measures the specific gravity of a liquid. |
| Hygrometer | Measures atmospheric humidity. |
| Lactometer | Measures the purity of milk. |
| Thermometer | Measures temperature. |



