A Arduino Board with ADC sampling frequency > 26 khz

I Have a sensor that needs sampling frequency to be equal 26 khz.

i have written the Arduino code that takes these values and sends to server with the help of esp8266

i don't want to shift to a new microcontroller (embedded programming)

The fastest the ADC clock can run with 10-bit resolution is 200 kHz and it takes 13.5 clock cycles to complete a reading so that's 14.8 ksps (kilo-samples per second). To get 26 ksps you will need the ADC clock to run at 351 kHz or higher. The prescale factors limit the choices on a 16 MHz Arduino to: 8 MHz, 4 MHz, 2 MHz, 1 MHz, 512 kHz, 256 kHz, or 128 kHz. You will need to use 512 kHz (slowest value faster than 351 kHz). At 200 kHz you lose 2 bits of accuracy (leaving 8 bits) and at 1 MHz you lose 4.5 bits of accuracy (leaving 5.5 bits) so I expect you can count on about 6 or 7 bits of accuracy.

You can tell the ADC to start a conversion on the Timer/Counter1 Output Compare Match B which should allow you to sample at 26 kHz (or very close, depending on how the math works out).

Good luck!

Note: You can get external ADC devices that can sample much faster and with higher accuracy if you need it.