Breaking Down the AtmosVue™30 Specifications (what they actually mean)

When you look at a spec sheet for a weather sensor such as the AtmosVue™30, you’re typically presented with a lot of numbers and technical terms. For example, these might include:

• Present weather outputs
• Background luminance measurement range
• Operating temperature range

But what does all this actually mean?

In this blog article, I’ll break down the key specifications for the AtmosVue 30 and explain what they tell us—in simple language.

Background

Before we get started, it’s important to note that the AtmosVue 30 consists of three separate sensors: the CS125 Present Weather and Visibility Sensor, the CS140 Background Luminance Sensor, and the HygroVue™5 Digital Temperature and Relative Humidity Sensor. In this article, I’ll share information about the AtmosVue 30 spec sheet, but please add a comment below if you want similar information on any of the sensors that make up the AtmosVue 30.

Key AtmosVue 30 Specifications

Maximum Reported Visibility

For the AtmosVue 30, the maximum reported visibility is 100 km (62.1 mi).

Maximum reported visibility tells us how far a person at the airport (pilots, air traffic controllers, or other aviation users) can see horizontally at a height of 2 m (6.6 ft) above the ground in the current weather conditions.

Background Luminance Measurement Range

For the AtmosVue 30, the background luminance measurement range is 0 to 45,000 cd/m².

Background luminance helps us understand how strong the contrast is between the runway lights and the background ambient light levels of the sky—a critical measurement because it determines how far a pilot can see as they land at the airfield.

Background ambient light levels are measured as a human eye would see them using the International Commission on Illumination (CIE) spectral response. In other words, it “sees” light at the same wavelengths you or I would.

Using the background luminance, we can determine how we need to adjust the methods used to calculate visibility in all light conditions, especially low-light or low-contrast conditions. Measured in candelas per square meter (cd/m²), background luminance, paired with other measurements in a larger calculation, can help determine aviation visibility.

Present Weather Outputs

For the AtmosVue 30, one output offers 57 SYNOP present weather codes and associated Meteorological Aerodrome Reports (METAR) and National Weather Service (NWS) present weather codes, as well as past weather codes.

The World Meteorological Organization (WMO) developed standardized practices to communicate weather data internationally without the need to translate weather information into different languages. This communication system, in part, uses numeric codes called SYNOPs. Transmitted at a regular frequency (usually every three or six hours), SYNOP codes can describe every significant present weather event at the site. For example:

• SYNOP Code 99 = Tornado
• SYNOP Code 61 = Slight Rain

However, the present weather sensors only transmit the highest impact code present at the time of the observation. In other words, if you had conditions with slight rain and a tornado at your airfield, only SYNOP code 99 would be transmitted.

While there are 100 different SYNOP codes, automated sensors are only able to determine a finite number of those codes. The AtmosVue 30, for example, can measure 57 of the codes.

Meanwhile, some airports are using other coding practices, such as METAR and NWS codes. METAR codes might use “FG” to indicate fog. NWS codes take the reduction a step further and might transmit just “F” for fog.

For the AtmosVue 30, another present weather output identifies standard present and past weather as mist, fog, drizzle, freezing drizzle, drizzle and snow, rain, freezing rain, rain and drizzle, rain and snow, snow, and hail.

Present weather sensors can determine a host of precipitation and visibility measurements. This spec is telling us not only what events are currently happening, but also what events occurred in the recent past.

Precipitation Intensity

The AtmosVue 30 can measure precipitation intensity.

The sensor measures precipitation intensity based on how much precipitation would fall if the rain, snow, or other precipitation event continued non-stop for a full hour.

Precipitation Accumulation

The AtmosVue 30 can measure precipitation accumulation.

This spec tells us the total amount of precipitation accumulation that has occurred since it was last reset (usually every 24 hours). For frozen precipitation, this is determined using a liquid water equivalent (LWE) ratio.

Operating Temperature Range

This sensor suite offers a large operating range, ideal for temperatures between -40 and +70°C.

If you’re anything like me, there is a temperature range that you’re most comfortable in. Too cold? You might bundle up with socks and a steaming mug of hot chocolate. Too warm? You might cool down with a fan and an ice-cold glass of water.

Like us, sensors are at their best when they operate within a specific temperature range.

Material

The AtmosVue 30 is constructed of stainless steel and hard-anodized aluminum that is powder coated.

In part, sensor durability and “ruggedness” are dependent on what materials are used to make the sensor’s outermost shell. In this case, the AtmosVue 30 spec tells us that it is suitable for even the most extreme environments, such as saltwater marine or coastal locations. The shell is designed to protect the metalwork and electronics inside.

Electronics Supply Voltage

The AtmosVue 30 requires 12 or 24 Vdc.

Volts direct current, or Vdc, tells us how much power is needed to operate the sensor.

Serial Interface

The AtmosVue 30 can be transmitted via RS-232 or RS-485.

This tells us that the sensor is flexible, and that data can be transmitted in two ways: over RS-232 or over RS-485. RS-232 is great for short distance communications. RS-485 is ideal for data transmission over longer distances and/or in environments with other electromechanical noise, which can cause issues if the signal is not sufficiently robust.

Why do these specs matter?

Each of these specs plays into the overall mission:

1. Keeping all aviation users, including the passengers and crew, safe
2. Giving accurate, timely data to controllers and other aviation professionals
3. Operating reliably in various weather conditions, giving you peace of mind

Final Thoughts

When you read a spec sheet, you’re seeing more than just numbers; what you’re seeing is performance. The AtmosVue 30’s specifications tell a story of the current and past weather conditions at an airport through a ruggedly tough, smart, and reliable sensor built for the future of aviation.

Credits: Richard McKay of the Campbell Scientific Ltd. regional office contributed to this article.

If you have any questions or comments, please share them below.