*** QVAR sensing - A new concept of sensor in ST portfolio ***

[Eleon BORLINI]

A new sensor has been recently launched on st.com, embedded in existing pressure and iNemo sensors: an electrostatic sensor that can be used for human presence and motion detection, touch detection, and user interface (UI) applications

Qvar stands for electric charge (= Q) variation (= var). It is an electrical potential sensing channel able to measure the quasi-electrostatic potential changes. ILPS22QS and LSM6DSV16X sensors allow to connect an analog input and convert it to a digital signal for embedded processing. In addition, the embedded Qvar channel can be enabled for sensing in applications such as water leakage detection, tap, double tap, long press, and L/R - R/L swipe.

[Eleon BORLINI · Accepted solution]

Additional information can be found on:

• Application note AN5755: Qvar sensing - Application note (st.com)
• ILPS22QS datasheet: Datasheet - ILPS22QS
• LSM6DSV16X databrief: Data brief - LSM6DSV16X

Share your comment here below, if you want!

[kSun.1]

I am very interested in this Qvar. What i understand is this Qvar depends on the electrode discharge and the Qvar wants to take advantage of ESD, is it correct? Also Does the Electrode pad size affect sensing ability? Do we always need ESD Diode to protect the Chip ?

[Eleon BORLINI]

Hi @kSun.1​ ,

The ESD diode are mandatory to protect the QVAR lines from electrostatic and electromagnetic discharges that goes beyond the absolute maximum rating that the QVAR can withstand. The dimension of the electrode pad affects the "wireless" electric field sensing, while it is pretty negligible for the QVAR contact sensing.

-Eleon

[marti3110]

I have a X-NUCLEO-IKS4A1 board connected to a STM32F401RE nucleo board and I also have the detachable add-on board STEVALMKE001A, which hosts the Qvar swipe electrodes. When I flash DataLogExtended firmware in Nucleo board and open Unicleo-GUI or MEMS Studio I enable Qvar buttom but the value I see is constant and, even if I touch in rapid succession one button and the other, the value never changed (is -420.103 mV when i select the LSM6DSV16X sensor and -860.366 mV when I select LIS2DUXS12 sensor). What can be the problem?