The fingerprint is the user's first choice for unlocking their phone, authenticating mobile payments, authorizing purchases, and unlocking applications by simply placing their finger into the sensor.
You may sometimes have noticed that when you charge your phone and try to use the fingerprint sensor for locking and unlocking your phone, it does not work. Sometimes it works after several attempts, and sometimes it stops due to too many attempts and forces you to unlock using an alternative such as a pattern lock or password, face recognition, etc. Again when you unplugged the phone from the charger, it started working again. So, let's take a look at what might be affecting the fingerprint sensor while it's charging.
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It is important to note that the majority of smartphones use capacitive fingerprint sensors. Electricity is used by capacitive sensors to determine fingerprint patterns. When you place your finger on the sensor, it measures the charge, then the ridges exhibit a change in capacitance, and these data are mapped out prints, allowing you to unlock/lock and authenticate.
Reason for the fingerprint sensor problem while charging phone
Let's discuss some of the reasons:
Irregular power supply
Due to fluctuations in power supply, you may experience any sensor of your phone stopping working and tapping randomly, as well as the fingerprint sensor ceasing to function.
Sometimes poor isolation between the component can also cause the problem.
Apple Forum also talks about it Read here
Using non-Standard charger.
Nonstandard chargers may not be able to deliver the proper amount of power and current to the sensor, which could be the cause.
Using nonstandard USB Cable /Thunderbolt cable
When using a nonstandard USB cable, the required specifications for a capacitive sensor, such as a fingerprint sensor, are not always met.
Dirt, Dry, Oily
When your finger is wet, dry, dirty, or oily, the fingerprint sensor does not work properly.
To get rid of these problems here are some solutions.
Always connect your charger to a stable and clean power supply where the voltage does not fluctuate.
It is always recommended to use the original charger supplied by the manufacturer. In addition, if the charger is damaged, always purchase the charger from the verified retailer showroom.
Always use the standard original USB cable and thunderbolt cable that came with your smartphone when you purchased it.
Before attempting to use the fingerprint sensor, clean your finger.
Restart your phone; hardware and software glitches can also be the source of the problem.
Update your fingerprint sensor software on a regular basis if provided via software updates.
Call for the official phone help desk if the problem is getting worst.
If the same problem repeats and becomes worse then you can take it to the repair center.