I got the circuit working now without the ADC, thats the one I will use.
BUT,I also tried the ADC, it only works in 10 bit mode when I try the 8 bit mode, nothing appears on the LCD. Here the progrm, but before here is the two lines I changed for the 8 bit mode:

ADCON1 = %10000010
Define ADC_BITS 8 ' Set number of bits in result

why is this happening?

INCLUDE "modedefs.bas" 'Includes supoprt for PicBasic language
@ DEVICE pic16F88, INTRC_OSC, CCPMX_ON
OSCCON=$60 ' use internal 4MHZ osc

ANSEL = 0
CMCON = 7 ' Turn OFF the comparators so pins can be used as digital I/O-pins
ADCON1 = %00000010 ' Analog to digital configuration register (ADCON)
' Set PORTA to digital

' Define ADCIN parameters
Define ADC_BITS 10 ' Set number of bits in result
Define ADC_CLOCK 3 ' Set clock source (3=rc)
Define ADC_SAMPLEUS 50 ' Set sampling time in uS

ADCON1 = %10000010 ' Analog to digital configuration register (ADCON)
' Set PORTA to digital

'/////////////////////////
'// LCD configuration //
'/////////////////////////

DEFINE LCD_DREG PORTB ' Set LCD Data port
DEFINE LCD_DBIT 4 ' Set starting Data bit (0 or 4) if 4-bit bus
DEFINE LCD_RSREG PORTB ' Set LCD Register Select port
DEFINE LCD_RSBIT 1 ' Set LCD Register Select bit
DEFINE LCD_EREG PORTB ' Set LCD Enable port
DEFINE LCD_EBIT 0 ' Set LCD Enable bit
DEFINE LCD_BITS 4 ' Set LCD bus size (4 or 8 bits) '4 therefore put wire at 4, 5, 6 and 7 of LCD
DEFINE LCD_LINES 2 ' Set number of lines on LCD
DEFINE LCD_COMMANDUS 2500
DEFINE LCD_DATAUS 250
DEFINE CHAR_PACING 2000
pause 1000


'/////////////////////////
'// PIN configuration //
'/////////////////////////

TRISA = %11100111 ' Set PORTA to all input
TRISB = %00001100 ' Set PORTB to all output
PortA = 0

'///////////////////////////////////////////////
'// Variable Declaration and initialization //
'///////////////////////////////////////////////
Output_Pot var byte
OldOutput_Pot var byte
Revolution var word
counter var byte

revolution = 0
Output_Pot = 0
OldOutput_Pot = 0
counter = 0

'Get initial value
'ADCON0.2 = 1 'Start Conversion
ADCIN 1, OldOutput_Pot 'analog pin 1 (RA1) get the 8 bit result
pause 50
if OldOutput_Pot > 512 then
OldOutput_Pot =1
else
OldOutput_Pot =0
endif

Mainloop:

'ADCON0.2 = 1 'Start Conversion
ADCIN 1, Output_Pot 'analog pin 1 (RA1) get the 8 bit result
pause 50

'Calculate the distance
if Output_Pot > 512 then
Output_Pot =1
else
Output_Pot =0
endif

if OldOutput_Pot == Output_Pot then
goto Mainloop
endif
if OldOutput_Pot != Output_Pot then
counter = counter +1 'If oldOutput_pot is different then Output_pot
OldOutput_Pot = Output_Pot
if counter =4 then
Revolution = Revolution + 1
counter =0
endif
endif

lcdout $FE,1, "Counter:",dec counter
lcdout $FE,$C0, "Revolution:",dec Revolution
pause 150


GOTO Mainloop
end