Monitoring Engine Temperature/Humidity in Storage Using a Modbus Gateway
Date Published: October 8, 2012
Wireless Gateway Remotely Transmits Crucial Data
Recently CAS DataLoggers provided the wireless datalogging solution for a customer who needed to prevent damage and wear on several large replacement engines by monitoring them for temperature and humidity in storage. These engines were the only backups for replacing the equipment being used in the plant, so whenever they were discovered to have corroded due to excessive heat/humidity, the plant’s entire operation went offline and this quickly cost the plant thousands of dollars each time. The engines were stored in 3 metal warehouses, each about 40 ft tall, 250 ft long, and remotely spaced. Nearby was a main office which was wired internally with its own network isolated from each warehouse--the office was often unoccupied so the storage supervisor needed all the data to be accessible from all 4 buildings. The challenge was to get a signal through the metal shell to their interiors, so a wireless solution was necessary to quickly integrate the plant’s new wireless technology and which was ready to go right out of the box for immediate implementation.
The plant installed a Wireless AirGate Modbus Gateway bolted to the end wall about 15 ft from the ground in each of the warehouses. 3 E1-32 Temperature and RH% Probes were also supplied by CAS DataLoggers for connection with each wireless gateway’s 4-20 mA inputs, monitoring temperature from 0-100°C (32-212°F) and humidity from 3-95% RH. Users stripped the probe wires to make a pair of leads inserted into 2 of each gateway’s channels. Each probe operated on a 24VDC power supply. Wireless antennas were then placed on each warehouse on the side of the exterior walls 20ft off the ground, going through the walls to the AirGate inside so that an exterior enclosure was unnecessary. Wiring was then extended 125 ft into the middle of each building’s interior via existing heat output ducts and connected to each antenna.
The wireless multifunctional gateway enabled simple and transparent insertion of wireless branches into the customer’s existing wired RS485 network. Users could select from the gateway’s 4 operation modes: Modbus Master, multiplexer, USBRS485 converter, and simple wireless RS485 extension. Additionally, a proprietary protocol based on IEEE 802.15.4 facilitated operation in Star mode, enabling the connection of several wireless segments to the existing Modbus RS-485 network.
The AirGate featured up to 16 operating channels and a maximum transmission power of 100 mW. Bright LEDs gave users clear status indication. Operating on a 10-35 Vdc power supply, the gateway could achieve an RF data rate of up to 250 Kbps and a serial port baud rate of 1200 to 115.2 Kbps. Using an operating band of ISM 2.4 Ghz and an antenna gain of 2 dBi, the AirGate's wireless range easily covered the 250 ft length indoors and ranged to 3280 ft. (1000m) outside to link all the remote buildings.
The wireless gateway used a network identifier (PAN ID) for transparency and ran at a broad operating temperature of 0 to 70°C (32°F-158°F). Additionally, the AirGate was an effective low-power solution with a power consumption of only 70 mA (@24 Vdc).
The AirGate also included an RP SMA female connector plug and two RS485 connectors for Modbus RTU interface. Data collection was easy with the gateway’s Mini-B USB device. Additionally, the gateway’s wireless capability was protected by strong security, utilizing powerful AES-CBC-128 Data cryptography (Advanced Encryption Standard).
Using the AirGate wireless gateway’s many features, the plant tied each warehouse into the office’s network for effective remote monitoring. The storage supervisor was then able to remotely monitor the engines’ temperature and humidity levels from anywhere in the plant’s 3 storage buildings or the office, which allowed him to better service the engines and led to fewer incidents of faulty engines. This cost savings alone paid for the gateway many times over and streamlined the plant’s operations.
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- Custom Data Loggers
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- Temperature Monitoring
- USB Data Loggers
- Wireless Data Loggers
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