Hygrometers are instruments used to measure the relative humidity of the air. In simple terms, they determine how much moisture is in the air. Two main types of hygrometers are commonly used: mechanical hygrometers and electronic hygrometers.
Mechanical Hygrometers
Mechanical hygrometers use a combination of materials that absorb moisture and react to the changes in the moisture levels. A small strip of hair from a horse or human, known as a hygroscopic material, changes length in response to the amount of moisture in the air. The hair expands as humidity rises and contracts when humidity falls. This movement in hair is connected to a pointer or needle that displays the readings on a dial.
Many mechanical hygrometers also use a small piece of cellulose that swells or contracts depending on the humidity level. The cellulose acts as a humidity-sensitive element, and the changes in its dimension are transferred to an indicator needle or pointer.
Electronic Hygrometers
Electronic hygrometers work by using a sensor that detects moisture levels. The commonly used sensor is a capacitor that reacts to humidity level changes. There are two plates in the capacitor that hold an electrical charge. The moisture in the air interacts with the plates, and as the moisture levels change, the electrical charge changes. The changes in charge’s magnitude are detected and measured by the circuit board, which displays the readings on the display.
Another type of electronic hygrometer is a resistive hygrometer. It consists of two thin-film electrodes with a layer of a polymer that absorbs water vapor. The film’s electrical resistance changes when it is exposed to different moisture levels, and this change is interpreted and displayed on the digital display.
Maintenance of Hygrometers
Regardless of the type, hygrometers work most efficiently when they are periodically checked and calibrated. Calibration is necessary to ensure that the instrument is measuring the moisture levels accurately. Inaccurate readings can happen over time due to dust, dirt, or humidity interfering.
A simple way to check if a hygrometer is accurate is to place it in a sealed plastic bag with a damp sponge for a minimum of 4 hours. The hygrometer should register close to 100% humidity. If the reading is more than 5% above or below, then it is time to recalibrate the instrument.
Recalibration is done by adjusting the calibrating screw or button on the hygrometer. Follow the manufacturer’s instructions when recalibrating to keep the instrument in good condition.
In conclusion
Hygrometers are essential tools that help maintain an appropriate level of humidity, especially in temperature-controlled environments. Mechanical hygrometers are generally inexpensive and straightforward to use but require frequent checks and recalibration, while electronic hygrometers are more accurate and offer more features but are expensive.
Regardless of the type, ensure that the hygrometer is appropriately calibrated to avoid damage to the instrument and inaccurate readings.
How Do Hygrometers Work?
Hygrometers are instruments used to measure the relative humidity of the air. In simple terms, they determine how much moisture is in the air. Two main types of hygrometers are commonly used: mechanical hygrometers and electronic hygrometers.
Mechanical Hygrometers
Mechanical hygrometers use a combination of materials that absorb moisture and react to the changes in the moisture levels. A small strip of hair from a horse or human, known as a hygroscopic material, changes length in response to the amount of moisture in the air. The hair expands as humidity rises and contracts when humidity falls. This movement in hair is connected to a pointer or needle that displays the readings on a dial.
Many mechanical hygrometers also use a small piece of cellulose that swells or contracts depending on the humidity level. The cellulose acts as a humidity-sensitive element, and the changes in its dimension are transferred to an indicator needle or pointer.
Electronic Hygrometers
Electronic hygrometers work by using a sensor that detects moisture levels. The commonly used sensor is a capacitor that reacts to humidity level changes. There are two plates in the capacitor that hold an electrical charge. The moisture in the air interacts with the plates, and as the moisture levels change, the electrical charge changes. The changes in charge’s magnitude are detected and measured by the circuit board, which displays the readings on the display.
Another type of electronic hygrometer is a resistive hygrometer. It consists of two thin-film electrodes with a layer of a polymer that absorbs water vapor. The film’s electrical resistance changes when it is exposed to different moisture levels, and this change is interpreted and displayed on the digital display.
Maintenance of Hygrometers
Regardless of the type, hygrometers work most efficiently when they are periodically checked and calibrated. Calibration is necessary to ensure that the instrument is measuring the moisture levels accurately. Inaccurate readings can happen over time due to dust, dirt, or humidity interfering.
A simple way to check if a hygrometer is accurate is to place it in a sealed plastic bag with a damp sponge for a minimum of 4 hours. The hygrometer should register close to 100% humidity. If the reading is more than 5% above or below, then it is time to recalibrate the instrument.
Recalibration is done by adjusting the calibrating screw or button on the hygrometer. Follow the manufacturer’s instructions when recalibrating to keep the instrument in good condition.
In conclusion
Hygrometers are essential tools that help maintain an appropriate level of humidity, especially in temperature-controlled environments. Mechanical hygrometers are generally inexpensive and straightforward to use but require frequent checks and recalibration, while electronic hygrometers are more accurate and offer more features but are expensive.
Regardless of the type, ensure that the hygrometer is appropriately calibrated to avoid damage to the instrument and inaccurate readings.