Page 51 - Occupational Health & Safety, November 2017

method, typically zip-ties or screws. This may include integrated mounting holes or brackets, the latter enabling a logger to be removed for data download.
BLE Versus USB Loggers
Researchers weighing BLE and USB field temp/RH data logger options should con- sider a range of important factors.
Cost of ownership: Even if BLE temp/ RH data loggers carry slightly higher price tags, they can cost less to own if research- ers only require a couple data loggers; since users don’t need to buy computer software or a base station, all they need is the free app running on their mobile de- vices. However, for larger studies involv- ing dozens of loggers, the extra cost of peripheral equipment required for USB temp/RH data loggers becomes less of a factor. Additionally, users already employ- ing USB loggers can continue using their existing base stations and software. Never- theless, the convenience and potential to significantly streamline both data logger deployment and data retrieval in the field using BLE may justify the cost of migrat- ing to this newer technology.
Data access: For outdoor field monitor- ing, data access can be a critical issue—es- pecially in hard-to-reach or limited-access locations, such as bird nests, tree canopies, bat caves, or fragile habitats. USB temp/ RH data loggers, which need to physically connect to a computer or device to down- load data, can be more difficult to use. By contrast, BLE temp/RH loggers let users transmit data wirelessly to mobile devices up to 100 feet away, eliminating the need for physical contact.
Data sharing: Researchers using pro- grams such as Excel on their laptop com- puters may find that USB loggers, which di- rectly offload data to the laptop, save them time. For users that want to share data files via the internet, BLE temp/RH data loggers may serve as a more effective option, since they work with mobile devices. The logger app on a mobile device can easily convert data into Excel or text files, and work with other mobile apps to share these files via email, messaging, or Google Drive.
Alarm notifications: Both USB and BLE logger models provide alarm notifications. With BLE loggers, however, the app can highlight which (if any) loggers in the area
have exceeded limits, so users can offload and review data from those loggers first.
Radiation shield integration: Many ap- plications require data loggers to be pro- tected from direct sunlight to prevent false high readings from heating caused by solar radiation. Both USB and BLE temp/RH data loggers have cables/probes that can easily be placed inside a radiation shield. BLE options, however, let users mount log- gers inside a shield and not have to remove them for download data.
Summary
There is no one right answer in choosing USB or BLE temp/RH data loggers for field monitoring. Instead, by evaluating the fac- tors outlined here, researchers can deter- mine the best approach for their projects.
Paul Gannett, product marketing manager at Onset Computer Corporation (www.on- setcomp.com), has more than 30 years of experience developing, marketing, and using data loggers and data acquisition systems.
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