Measuring 16 Temperatures Remotely

In several cases, one cannot access the area where the temperature needs to be monitored. For instance, the temperature inside a kiln may reach a few thousand degrees, which is beyond the tolerance of humans. Environment chambers may need to be completely sealed off when operating, which means monitoring the conditions within has to be remotely accomplished. Simpler cases may also be considered, where the computer logging the temperature is in a central location, whereas the monitored sites are spread out in different rooms.

The ideal instrument should allow measuring temperatures over a local or remote network, with a built-in web-server to access the instrument, requiring neither programming or app. Measurement Computing has just the instrument and it is the WebDaq-316, a stand-alone temperature logger that allows the user to measure temperatures on 16 channels using J, K, T, E, N. B, R, or S type thermocouples. The user can access the instrument through its web-server over a local or remote network.

With 3 GB of internal acquisition memory, the WebDaq-316 acquires samples at the rate of 75 samples/sec. However, if the memory is insufficient for the job on hand, the user can add more by inserting two USB flash drives or an internal SD memory card. The measurement data can be transferred from the SD card, flash drive, or the internal memory. Alternately, the user can download the acquired data from the web-server as well. It is easy to import the data to an analysis software or a spreadsheet as the WebDaq stores data in CSV format.

The user can operate the WebDaq-316 in two modes—normal or high resolution. In the normal mode, the instrument works at 75 samples/sec or 78 Hz maximum, whereas in high-resolution mode, it can scan at less than one sample/sec across all channels. In the high-resolution mode, WebDaq-316 drops its bandwidth to 14.4 Hz, which also lowers its noise and gain error. That allows the 24-bit delta-sigma ADC on the instrument to operate at its peak efficiency.

The web-server has the ability to send SMS texts or e-mail messages. Therefore, the user can receive an appropriate notification whenever a temperature moves out of limits. Additionally, there are four programmable digital IO channels on the WebDaq-316. The user can make use of these IO channels to operate some local activities such as trigger an alarm or shut down equipment. As the IO channels are programmable, they can be inputs or outputs. As inputs, they can act as trigger depending on external signal, and as outputs, they can trigger alarms. The channels are available on terminal strips on the front panel, which makes all T/C and DIO connections easier.

The user can assign measurement operations through jobs and schedules. For instance, the user may want to change jobs or sample rates whenever a temperature crosses the limits, or return to a schedule of lower rate when the temperature returns within the limits. The user may also want to schedule jobs for triggering alarms or receiving notifications of such conditions.

Based on the Raspberry Pi compute module, the WebDaq-316 operates on a DC power source of 6 to 16 V. This allows vehicular operation as well.