how does a humidistat wprk?

Question

Can it be calibrated without expensive test equipment - and how?

Answer 1

I don't know what sort you have, but traditionally they are made with a fiber (human or horse hair was popular) that has the property of changing it's length based on humidity. So, for hair, which has proteins with hydrogen bonds that 'relaxes' or 'constricts' based on how much water vapor is present to interfere with the bonding, you simply measure how much the hair stretches as the humidity changes.

To calibrate a humidistat, you can look up and make solutions of various salts in water at known concentrations that will have a partial pressure of water (humidity) and enclose the humidistat in a container with one of those solutions in equilibrium.

You would of course also have to maintain a known temperature.

Answer 2

The Piano Life Saver System is made up of basic components which work together to control the humidity levels within your piano, maintaining the recommended relative humidity, no matter what the external conditions are.


HOW THE COMPONENTS WORK TOGETHER





Through a cycling action, the Humidistat is calibrated to create a separate environment within the piano, producing a narrow range of average humidity. When the Humidistat, located less than an inch from the soundboard, senses that the wood is dry, it turns the Humidifier on. Then, when the Humidifier has provided enough moisture to the soundboard, the Humidistat turns off the Humidifier and turns on the Dehumidifier. The Dehumidifier carries away moisture from the soundboard on air currents until the Humidistat senses that the soundboard is dry. The System again switches to the humidifying function. The cycle continues day after day, year after year, protecting your piano from external conditions.

Answer 3

Humidistats, well at least electronic humidistats, operate on the prinicipal that damper objects conduct electricity better. The device then calculates the humidity based on the resistance of the sensor. They are calibrated with a resistor that corresponds to a specific humidity. In general, only good humidistats allow for calibration, and in that case, you need the calibrator resistor. It should not be expensive to do.