Teardown and tryout: Wireless temperature/humidity module

October 01, 2013 // By Martin Rowe
Fall is here, and that means heating season will soon arrive – or, depending where you are located, may already be here. If you have an acoustic guitar, you know that humidity – or lack thereof – is the enemy.

That's why I keep three plastic film canisters with sponges in my case to keep the humidity up. But the sponges dry out. Wouldn't it be nice to know when the sponges need more water without having to open the case?

That's where a wireless temperature/humidity logger can help. The WiFi-502 temperature/humidity logger from Measurement Computing has 802.11b WiFi and USB connectivity. Having an evaluation unit on hand, I decided to use it.

The Wifi-502 comes with a micro-USB cable, which you can use to perform initial setup once you download and install the EasyLog software. Installing the software and connecting to my XP laptop was a breeze. The installation needed Microsoft .NET Framework 2.0, which downloaded and installed automatically.

With the software installed, I connected the logger using the supplied micro-USB cable. The system found the new hardware and connected to it. A setup screen then appeared that let me select temperature units, set high and low alarms (for both temperature and humidity), and set a sample rate and number of samples per transmission from the logger to the host computer. The default is 10 seconds between samples and six samples per transmission to the host. Temperature range is -20°C to +70°C.

Once you establish a wired connection, you can set up a wireless connection to your local network and disconnect the cable. Once the wireless connection is established, you can configure the module without the USB cable, which becomes a charge cable only. (The cable works with an iPhone charger.) Figure 1 shows the logger and the initial PC screen, which includes a live image of the logger's display. You can run multiple loggers with one network.

Figure 1. A networked temperature and humidity logger transmits data to a computer on the network. The difference in temperature between the logger and the computer occurred because the logger doesn't transmit in real time.

Figure 2 shows the operating screen.