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Alternative Weather Stations

Weather has been around a long time. In fact, the first precipitation fell to the earth about 4.5 billion years ago and likely included high concentrations of iron. (For those with pocket protectors, that was intended to be humorous.)

Measurements of temperature and weather conditions have evolved as our technical sophistication has increased. Today, there are many companies making instruments that measure and record many different climate, weather, and natural resource parameters. The problem for the weather consumer, though, is navigating the gap between two weather instrumentation price extremes. (Which is why you’re going to love Dyacon, but we’ll get to that in a minute.)

Highly Technical and Über-Scientific Weather Instrumentation Companies

While they haven’t been around as long as the first precipitation, companies like Campbell Scientific, Vaisala, RM Young, Sutron, Luft, and others are well established organizations. Although the weather instruments available from these companies is extensive, installing and programming a weather station built on these components is typically beyond the skill (or interest) of most users. In general, these stations require trained field technicians and application engineers to get the system up and running, as well as to keep it maintained. Such solutions leave the user dependent on the reseller or manufacturer to update and maintain the system.

Low-Cost (Cheap) Weather Instrumentation Companies

Some companies, such as Davis Instruments and Oregon Scientific, have focused on low-cost weather instruments, often made in countries with very low labor costs. Such instruments will seem to be less expensive than alternatives, but the costs and frustrations can add up as users are left to replace components (or the whole system) over short amounts of time.

Frustratingly, buyers of weather stations are typically left to choose between a low-cost (read: cheap) weather station from a department store or a very high-cost scientific instrument that may require a government grant to buy.

The Perfect Middle Ground: Dyacon Weather Instruments

Dyacon offers an alternative weather station system that uses high-end instrumentation elements in an integrated, easy to use package. Weather stations from Dyacon are lower cost than “research-grade” solutions and are superior to department store instruments. Dyacon stations are shipped preconfigured, with no programming required. If you can install a home light switch and set the clock on your microwave, you have what it takes to install, expand, and maintain a Dyacon weather station.

Dyacon weather stations are designed and manufactured in the US to meet the needs of those who need reliable weather data in a cost effective, practical solution.

Feel free to drop us a note or give us a call if you have any questions.

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SDI‑12 was originally developed in 1988 for microprocessor-based environmental sensors. In 1992, the SDI‑12 documentation was refined by NR Systems, under contract with the U.S. Geological Survey. The intention was to provide a common sensor interface for environmental data collection equipment. The SDI‑12 technical committee continues to maintain the standard.

Electrically, SDI‑12 uses a single 5 V signal line at a fixed data rate of 1200 bps. While slow and not as electrically robust as RS‑485, the protocol has been used widely in its niche application due to the stability and universal compatibility defined in the protocol. The protocol also allows for very lengthy measurement processes that can take up to 30 seconds to complete.

The master-slave architecture can have 10 sensors or more connected to the same SDI‑12 port.

What do sensors connect to?

Data Loggers
Many data loggers include an SDI‑12 interface. Dyacon THP‑2 and WSD‑2 can be used with SDI‑12 data loggers.

SDI‑12 Verifier
NR Systems maintains a tool for development and validation of SDI‑12 sensors. The accompanying software includes some data logging capability, but the cost and data format make this solution largely impractical for most data logging applications. A new release of the software will improve data logging capability, but the release date is not known.

PC Utilities
A number of SDI‑12 to USB or RS‑232 adapters are available. None of these have been evaluated, so no recommendations can be provided at this time.

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Modbus is a data transmission protocol developed by Modicon in 1979 for industrial control applications. It uses a master-slave architecture, where one device is in charge and requests information from multiple (slave) devices. Modbus is a simple command and control protocol that has been adapted to a number of media including TCP/IP, SMS, and wireless transceivers. Modbus is widely used for low-power, industrial controls.

Modbus is an active standard and is documented by the Modbus Organization. Wikipedia also has a brief article on Modbus.

RS‑485 uses a balanced electrical signal. It is very tolerant of electrical noise, Ethernet and USB use similar signal levels.

Dyacon air sensors (TPH‑1) and wind sensors (WSD‑1) use Modbus RTU frame over RS‑485 at a default data rate of 19200 kbps. The data rate was selected as a balance between low power and long cable runs, allowing for runs of over 1000 ft. The data rate may be set between 1200 bps and 38400 bps. Cat‑5 cable is a low-cost solution for extending the sensor cables.

Multiple Modbus RS‑485 devices can be connected to a single data bus. Each Modbus slave device has a unique address. The master sends a “read” request to a specific device address. The slave device responds with the requested data. TPH‑1 and WSD‑1 sensors are Modbus slave devices and must be connected to a master.  Dyacon user manuals contain the necessary information for programming the master device.

The address, data rate, and calibration settings on Dyacon Modbus sensors can be configured through Modbus commands. No special programming software is required.

So what can the sensors connect to?

Dyacon Control Modules
Dyacon control modules (CM‑1 and CM‑2) include ports for WSD‑1 and TPH‑1 Modbus sensors. No programming and no configuration are required. The control modules are the basis for the Dyacon MS‑100 series weather stations.

PC Utility
One of the programs Dyacon uses is Modbus Reader from KurySoft. The companion program Modbus Constructor builds an interface for the sensor. The reader program can then be used license-free on any computer. The reader can send and receive messages for configuring and testing the sensor. Feel free to contact Dyacon if you would like a copy of this construction file for your use.

Modbus Reader also has logging capabilities, but it is not recommended for SCADA or critical data logging functions.

Programmable Logic Controllers (PLCs)
PLCs are industrial automation controllers. These universal controllers are used to control process equipment such as a production line for baking cookies, processing pharmaceuticals, or making circuit boards. They can also be used for automating lighting, pumps, or HVAC environmental controls.

The 24 VDC power input on the Dyacon sensors and control modules allows them to directly connect to PLC controls and power supplies.

Environmental Data Loggers
Data loggers record sensor inputs into local memory for later retrieval and analysis. Many data loggers have multiple analog or digital sensor inputs. Many data loggers will include Modbus RS‑485 host capability.

Please give us a call if we can answer any questions or help you evaluate the best solution for your application.

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Design and development of the wind sensor WSD‑1 has been an interesting journey. The design was started in January 2013, and the first production run was ordered in January 2014. Several design iterations have been produced. Along the way, several images and videos have been captured.

A few of these have been combined into the following short video presentation:

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Getting field time for the wind sensors has been a priority from the beginning of the design effort. The following images are a collection of how they fare in some of the cold and snowy conditions.

The first image shows several design variants. The red one was the first design. Drip edges were introduced in the next iteration. The vane fin and anemometer cups were initially 3D printed. A number of cup designs were tested before tooling the injection mold.

Three WSD variants on the test mast.

Three WSD variants with snow.

WSD-1 head on w/ snow.

Several cold, dark, and foggy days led to an accumulation of frost. A slight breeze was just enough to turn the cups but not dislodge the ice crystals.

Frosty anemometer and vane are still operational.

Snow is always a challenge.

Snow accumulation on solar panel.

Snow accumulation melts off a bit.

Snowed in wind sensors did not freeze. The still morning air gave way an hour later, and the cups then turned freely.

Not frozen, just snowed in due to still air.

With all the time and care we put into their existence, each of our products quickly becomes our “baby.” It’s hard to abuse something so near and dear, but for product designers like me, this type of testing is necessary. We did a couple of rounds of wind tunnel testing on a WSD-1 (the Dyacon wind sensor) using an ELD wind tunnel with an 18″ square test chamber. We tested the sensor up to 60 m/s (134 mph, 215 kph).

Tests were structured around ISO 17713‑1. The tests conducted were:
– Starting threshold
– Transfer function
– Distance constant
– Off-axis response ratio

The ISO 17713‑1 tests were adapted to meet the digital output characteristics of WSD‑1. Additional testing at an independent lab is planned.

The following are some images from the effort:

Wind sensor in wind tunnel test section

A computer is used to capture the raw RS‑485 data during testing. These data will then be used by the firmware to calculate wind speed and direction for the Modbus data frame.

Computer used to capture RS485 data.

The test section floor and sensor mount allow the sensor to be tilted at 5 degree increments to a maximum incline of 30 degrees forward and back.

Off-axis response test

How do you abuse a sensitive wind sensor? Mount it to your truck. Rain, snow, dust, salt spray, vibration, gusts, tree branches, and overhead structures have all been encountered. The sensor pictured has racked up more than 5,000 highway miles at road speeds up to 80 mph (128 kph). A sensor like this on your truck is enough to make you the envy of every geek on the road.

Truck with wind sensor mounted.

Drive safe.

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*NOTE: This blog post is out of date. Some information may no longer be relevant.*

The wind sensor is typically a fixture on my truck. It has traveled thousands of highway miles and drawn a number of curious looks. While some cool jocks have retro 1960s bed exhausts, I have an anemometer. I’m a proud geek.

Exposing the wind sensor to long duration high-speed wind and turbulence, vibration, dust, salt spray, and ice are the kinder treatments. As you can imagine, the elevated position of the wind sensor increases the likelihood that an absent minded driver will try to wipe the thing off on low structures. I’ve done this twice.

The following YouTube post gives the whole story.

Dyacon YouTube Channel

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