Monitoring a 12th Century Historic Church with NI Wireless Sensor Networks and LabVIEW

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"Using LabVIEW and NI WSN technology, the team easily implemented a monitoring system for a 12th century historic site. The flexibility to place the measurement systems in various locations while using multiple strategies and the ability to connect to a large variety of sensors was a great advantage."

- Juan José Cabana González, Diseño Implementación y Optimización OPIDIS

The Challenge:
Preserving a historical monument by monitoring environmental factors without altering the monument’s aesthetics.

The Solution:
Building a monitoring system for the Santa María de Mave Church using LabVIEW, NI wireless sensor network (WSN) hardware, and the NI WLS-9163.

Author(s):
Juan José Cabana González - Diseño Implementación y Optimización OPIDIS
Marian Chiriac - Fundación Santa María La Real
Jose M. de Uña García - OPIDIS

The Santa María la Real Foundation in Aguilar de Campo, Spain, developed a restoration project for the Santa María de Mave Church and its monastery, which date back to the 12th century. The project was financed by the Castile and León Regional government through the Románico Norte program, which supports the Santa María la Real Foundation and the Heritage Monitoring System program (MHS) and is financed by local action group País Románico through development programs of the Ministry of the Environment and Rural and Marine Areas.

After remodeling was completed for the historic church, the foundation recognized the need for continued monitoring to preserve the monument and proactively protect the church from environmental decay. As a result, the group developed a pilot program for monitoring the environmental parameters in the church, including the following:

  • Air temperature and relative humidity at 17 locations within the nave of the church
  • Air temperature and relative humidity on the church's exterior
  • Data acquisition from a compact meteorological station located in the upper part of the church
  • Measurement of structural vibrations

The church’s conservation team determined these measurements would have to be stored on a central computer located within the church and the data should be transmitted to a remote site for viewing and management. In addition, an infrared detector access meter, a fire detector, and a device to remotely control external equipment would need to be installed.

The team selected LabVIEW software to manage the entire system and execute multiple processes simultaneously. They also chose NI WSN technology for measuring temperature and humidity parameters, as well as for the access detectors, fire detectors, and the actuators. Also, the team used an NI WLS-9163 Wi-Fi module to measure structural vibrations with a triaxial accelerometer.

The team’s greatest challenge was installing wires and hiding the sensors to not disturb the monument's appearance while maintaining strong radio communications signals, which was difficult due to the monument's stone walls and pillars. Figure 1 outlines the location of the sensors network in the church's nave.

Figure 1: The Node Distribution Plan

The team installed two NI WSN-9791 gateways in a small room attached to the nave, effectively hiding the modules from a person’s view for aesthetic purposes. The team used high-gain external antennas (9 dB) and 1.5 m extension cords for the two gateways, which allowed for placement of the antennas near the wooden door in the separation wall to maintain maximum communication distance and reliability.

The team used NI WSN-3202 analog input nodes, which are power efficient and easy to connect, with model HMP50 temperature and humidity meters. These devices read the temperature and humidity every 10 seconds, then using LabVIEW WSN, they calculate an average each minute and transmit that average to the gateways. By also taking advantage of the programmable node capabilities and LabVIEW WSN, the team was able to achieve power saving benefits with the DIO lines as well. Digital inputs (channels 0 and 1) are only sent if changes are detected, and digital outputs activate solid state relays when messages are received from the gateway.

The development of the node programs in LabVIEW allows for the incorporation of complex functions in the nodes to ensure the survival of the node batteries and a high level of energy efficiency. For example, the conservation team can implement a strategy to only send data when there are changes based on averages or complex calculations. Also, the messages allow the team to implement remote configuration from the executables.

Originally, the conservation team installed the WSN-3202 nodes without a protective case, as shown in Figure 2. 

Figure 2: Measurement Node

Later, the team installed the nodes in a watertight casing, which can be painted and more easily hidden. This resulted in better positioning for radio communications.

Using LabVIEW to manage the measurement system, the team developed a multithreaded program with various processes executing simultaneously. The processes include the following tasks:

  • Measuring the data from the sensor network and the meteorological station
  • Reading data from the accelerometer channels
  • Sending the data to the remote database using an Internet connection
  • Managing the program's graphic interface

The processes are balanced between the different CPUs in the HP Proliant ML115 G5 server (one quad-core Opteron CPU). The application executable starts up as a Windows OS service using a utility called Service Keeper and Service Mill. Part of the interface is shown in Figure 3.

Figure 3: A Screenshot of the Interface

The conservation team installed a meteorological station connected to a serial cable (RS232, RS485, RS422, and SDI-12) to a Wi-Fi Serial Digiconnect Wi-SP device linked to a Wi-Fi access point. DIGI Realport software on the server emulates a serial port, and the LabVIEW application reads the station data at this serial port.

The team used a similar strategy to connect the WLS-9163 device reading at the three accelerometer channels. They connected the WLS-9163 Wi-Fi client to the access point, and LabVIEW reads from the analog input channels.

Using LabVIEW and NI WSN technology, the team easily implemented a monitoring system for a 12th century historic site. The flexibility to place the measurement systems in various locations while using multiple strategies and the ability to connect to a large variety of sensors was a great advantage. Using NI WSN hardware along with flexible LabVIEW software, the church conservation team achieved their goals and maintained the quality and integrity of an important historical treasure.

Author Information:
Juan José Cabana González
Diseño Implementación y Optimización OPIDIS
Angustias,34 2do izquierda
Valladolid
Spain

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