ws109

Ambient Weather WS-109 Keychain Altimeter, Barometer, Thermometer, Clock & Compass
Welcome to Ambient Weather's WS-109 support webpage. We provide you with the latest updates to the User Manual, downloads, Frequently Asked Questions (FAQs) and technical support contact information.

Downloads
[|WS-109 User Manual]

FAQs
Altitude is determined based on the measurement of atmospheric pressure. The greater the altitude, the lower the pressure. When a barometer is supplied with a nonlinear calibration so as to indicate altitude, the instrument is called a pressure altimeter or barometric altimeter. A pressure altimeter is the altimeter found in most aircraft. The calibration of an altimeter is of the form:  where c is a constant, T is the absolute temperature, P is the pressure at altitude z, and Po is the pressure at sea level. The constant c depends on the acceleration of gravity and the molar mass of the air.
 * Q: How does an altimeter work?**

Here is an excellent guide provided by REI: []


 * Q: The altitude changes when I am not moving. Why does that occur?**
 * A:** Altimeters are often misunderstood because they do not measure your actual position on the earth (true altitude) such as a GPS, but measure the air pressure and predict the altitude based on this measurement.

This is referred to as “Pressure Altitude”. Pressure Altitude is adversely affected by the true altitude and to a lesser extent, changes in the weather, often referred to as barometric pressure changes.

Thus, your Pressure Altitude can change without changing your position. These changes can be as great as a thousand feet (the changes due to weather are more pronounced at higher altitude).

To offset the difference between Pressure Altitude and True Altitude, you must calibrate the device at a known altitude, whenever convenient.


 * Q**: Where can I find a good pressure altitude calculator?
 * A:** Visit: @http://www.csgnetwork.com/pressurealtcalc.html


 * Q: How do I measure the sea-level pressure?**
 * A:** Once the unit is calibrated at a known altitude, the sea-level (relative) pressure does not vary and the measured (absolute) pressure fluctuates with the weather and altitude conditions. To determine the sea-level pressure, calibrate the pressure altitude at a known true altitude and the sea-level pressure will be accurate.

This behaves differently than a weather station barometer, which assumes a constant altitude, and the measured and sea-level pressures change together with a fixed offset (as determined from the alititude compenstation).


 * Q: The temperature sensor is inaccurate or slow to respond. Why is that?**
 * A:** The temperature sensor is housed inside the unit and the entire unit must heat up or cool down to a steady-state condition. This is known as the //thermal mass time constant//. The unit must be placed in an open area, out of the sun and away from your body to recieve an accurate temperature. Unfortunately, the temperature sensor can not be exposed to the elements and must adjust based on the thermal mass of the unit.

Also note that this is a prediction of future weather conditions and not a prediction of current weather conditions.
 * Q: The forecast icon does not appear to be accurate or it does not reflect current conditions.**
 * A:** The forecast icon is a prediction based on rate of change of pressure, and requires some historical context to predict the weather conditions. Allow at least 72 hours for changes in pressure to take place. Please note that the forecast is only a prediction based on rising or falling pressure, and is considered an estimation 24-48 hours in advance, and is not accurate and is considered simply a tool to predict the weather.

You must be fixed in one location for this function to accurately work. Once your altitude changes, the icon must be reset.


 * Q: Why does the altitude show single digits when the altitude is above 10,000 feet?**
 * A:** The unit only displays four characters to maintain its small size and large LCD. Thus, when the altitude exceeds 9,999 feet, the unit will not show the thousand foot number. Example, when the altitude is 10,050 feet, it will show 50 feet.


 * Q: Why does the altitude climb not display the negative sign when less than or equal to -1000 feet?**
 * A:** Due to LCD size constraints, the negative sign is not shown when the climb altitude is less than -999 feet.

A: The compass has failed. Visit [|AmbientWeather.com Returns and Exchanges]to replace this item under 1 year warranty.
 * Q: Compass reads E30.**