We occasionally hear from heavy users (who runs almost a hundred tags off a single tag manager at short logging interval) that "spikes" appear in the temperature or humidity graph. While this is sometimes caused by defective temperature sensor IC itself (which resolves by requesting a replacement tag) it may also be caused by bit-error in transmission in a noisy radio channel shared by many tags. By default, each tag uses 8-bit CRC implemented by firmware on top of a 16-bit CRC-CCITT by hardware. This provides an upper bound of undetected error rate of one in 16.8 million regardless of bit error rate of the raw radio channel. However, if each tag transmits once per minute and you have 100 tags, you may encounter an undetected error (which appears as a corrupted temperature data point or a spike in the temperature graph) every 116.5 days. 

To improve this, we have added an option to turn on 32-bit CRC error checking already implemented in the radio hardware.

This reduces the error rate to 1E-12 or one in trillion. Now you should not be getting any bit-error caused spikes in temperature/humidity graph. If after you turn on this option and migrated all tags, and you still have the spikes, contact support and we will email you a prepaid return shipping label to send back the tag for a replacement right away. 

Feb 10, 2016:

You can now edit the temperature or humidity graph by "click to remove point" like below. This will allow you to remove data points that you believe is bogus manually. After you are done, click the yellow "Save" button to permanently delete these data points. 

This feature is currently only available in the web interface on a PC or Mac. Go to https://mytaglist.com/eth then click the blue "Stats" on the bottom of the page and choose either "Temperature" or "Humidity". Zoom into the graph until it shows each raw data point. Then scroll to the bottom of the page to access these buttons. (If you do not see them press F5 key to force your browser to refresh its cached version of the page.)

‹ Go back to the blog

Comments

Leave a comment