Monthly Archives: April 2019

Wireless Sensor for monitoring Insulin Temperature

We are working on a wireless temperature monitor for Insulin. Insulin (like the one in the image below) needs to be stored between 2 and 8 degree Celsius. Insulin can be expensive. A single pack containing 5 NovoRapid insulin cartridges costs around Rs 2600 (about $37) . Insulin gets damaged if it freezes. It also gets damaged if exposed to high temperatures. An in-use cartridge can tolerate up to 30 deg C but it should be consumed within 4 weeks.

Even inside a refrigerator there can be lot of variation in temperature from one spot to another. Whenever the refrigerator door opens, temperature rises because of exposure to warm air from outside and it takes some time for the temperature to return to normal after the door is closed. In some refrigerators, the cyclic variation in temperature around the set point (which may be user settable) may result in temperature falling below zero during some part of the cycle.  For instance, a set point of say 2 degrees may result in temperature falling below zero and then rising above zero periodically.

Our solution is a small form factor, single CR2032 coin battery powered sub-GHz wireless node suitable for continuous temperature monitoring. The sensor sends ambient temperature and battery voltage to gateway node which in turn forwards this data to the cloud over WiFi.  A single gateway can handle up to 128 sensor nodes.

We are offering three variants –

  • With FCC certified radio.
  • With ETSI certified radio.
  • WPC/GOI compliant radio for India.

The images below show the tag without enclosure.


Low profile temp tag_smaller

We did not use a BT-LE (Bluetooth Low Energy) radio because of its limited range. These tags will usually be inside a refrigerator while the gateway may be in some other room (next to a wall socket). Sub-GHz radios operating at a low data rate (1.2 Kb/s) will provide a stable link in this situation where as 2.4 GHz BT-LE radios with data rate of 1 Mb/s will most probably not work.

Transmit Power is +10 dBm.  Receiver sensitivity at 1.2 kbps is -112 dBm.

Our solution provides 24/7 monitoring where as a BT-LE only radio talking to a cell-phone will be useful only when the cell phone is in range of the temperature tag.

WiSense offers a gateway with a sub-GHz radio interfaced to a Photon WiFi module.  Here’s a pic of our gateway. We also offer another version with internal antennas.




For more information on WiSense products, please visit