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Simple analog sensors require the host device to perform a number of calculations to correctly scale the inputs, check for errors, and convert to usable measurement units. Similarly, sensor measurements are typically averaged over several seconds, minutes, or hours in order to present useful measurements of conditions and trends. Instantaneous measurements can be misleading or jump around too much to be useful and must be averaged and limit controlled to minimize the inherent noise.

All of these calculations put a burden on the host device and the software developer. For applications such as PLCs, embedded devices, and computer software applications, analog sensors require the programmer to have an in-depth knowledge of sensor output, measurement characteristics, and weather parameters.

With an ever-present focus to keep things simple and user-friendly, Dyacon WSD‑1 and TPH‑1 present usable digital data to the host device. For example, wind speed can be used directly by the developer without the need to count pulses or scale the voltage and then test, average, and convert the output.

Dyacon WSD-1 and TPH-1 go a step beyond other digital sensors in that both sensors provide additional calculated values:

TPH-1 gives temperature, pressure, and humidity measurements. Output values have been sampled multiple times, checked, and averaged. As of the latest firmware version, a value for a 3 hour barometric pressure trend is also given.

WSD-1 provides wind speed and direction data. Similarly, these measurements are sampled multiple times, checked, and averaged to provide a current measurement. Extended data are now available, which give 2 minute and 10 minute averages of wind speed and wind direction. The 10 minute average is the typical period for weather reports. Other applications may find the current or 2 minute average values to be more practical.

The extended calculations of trend, 2 minute average, and 10 minute average are done along with other data processing on the Dyacon sensors. Since the sensors are specifically optimized for the target measurements, there is no significant power penalty for the extended measurement data. Low power applications, such as environmental data loggers, can reduce their overall system power budget with Dyacon sensors. The data logger can wake, store data, and return to sleep without having to collect multiple analog samples and perform the related calculations.

Creative management of limited power resources is very exciting stuff for us geeks. Oh, what fun! 😉

Eugene

Special events, such as athletic and motor races, large group camps, or outdoor meetings, can pose challenges for organizers as they try to manage resources and prepare for hazardous weather. High winds, cold temperatures, and lightning are common in our area and can increase the risk of injury. Similarly, high temperatures or high humidity can lead to deadly heat injuries.

Here in northern Utah, races such as Lotoja and Ragnar Relay pass through sparsely populated areas and high altitudes. Rapidly changing weather conditions can jeopardize the safety of participants, support crew, and staff, especially when the route may not be easily accessible to evacuation resources.

Dyacon weather stations can be temporarily deployed to key locations to provide quantitative information regarding changing weather conditions in advance of and during special events. Support crews may call in “cold” conditions, but actual weather data can help remove ambiguities and provide a concrete basis for management decisions.

Last week, I had an opportunity to help conduct a large group outdoor activity. Several climbing instructors and I provided an opportunity for 60 youth to take on a 150 ft (50 m) rappel. The venue was at 9200 ft (2800 m) altitude. While this altitude is not extreme, it did provide an opportunity to deploy a Dyacon MS-130 to monitor conditions at the peak while we conducted the group activity 300 feet below.

Event operators can receive weather reports via SMS text message or through Weather Underground. SMS is universally compatible with mobile phones and can be accessed in areas of marginal cell phone coverage.

If you are conducting an event and would like to utilize a Dyacon weather station, please give us a call. We would be happy to support your event.

Eugene

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.

Eugene

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.

Eugene

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.

Eugene

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:

Eugene