Delta Sigma ADC is inverting

[selbstdual]

Dear Readers.

Currently I am using the setup whose picture is attached. This is a Delta-Sigma ADC from AN700.
According to my calculation I adjusted it to measure an area of about 10 to 80% of the resistor's
value.

Unfortunately in exactly this area there is happening nothing, there's one value all the time.
If I am rotating in the area being defined as out-of-range there a distinction is made.

What could be the problem, what to change ?

My code in PicBasicPro:

Define OSC 8

;Variables
result_l VAR BYTE BANK0 SYSTEM
counter VAR BYTE BANK0 SYSTEM
result_h VAR BYTE BANK0 SYSTEM

;Register
OPTION_REG = 0
TRISA = $01


;Interrupts
INTCON = 0
VRCON = $EC
CMCON = $06

Start:
GOSUB Value
StartV = ADCValue
Pause 10
GOSUB Value
EndV = ADCValue
IF StartV = EndV THEN
Low GreenLED
High YellowLED
ENDIF
IF StartV != EndV THEN
High GreenLED
Low YellowLED
ENDIF
GOTO Start
END


Value:
GOSUB Value2
ADCValue = result_l * 256 + result_h
RETURN


Value2:
ASM
DeltaSigA2D
clrf     counter
clrf     counter+1
clrf     result_l
clrf     result_h
movlw    0x03    ; set up for 2 analog comparators with common reference
 movwf    CMCON
loop
       btfsc    CMCON,C1OUT ; Is comparator high or low?
       goto     complow      ; Go the low route
comphigh
       nop                      ; necessary to keep timing even
       bcf      PORTA,3     ; PORTA.3 = 0
       incfsz   result_l,f   ; bump counter
       goto     eat2cycles    ; 
       incf     result_h,f    ; 
       goto    endloop        ; 
complow
       bsf      PORTA,3   ; Comparator is low
       nop                      ; necessary to keep timing even
       goto     eat2cycles   ; same here 
eat2cycles
       goto     endloop    ; eat 2 more cycles
endloop
       incfsz   counter,f   ; Count this lap through the loop.
       goto     eat5cycles    ; 
       incf     counter+1,f  ; 
       movf     counter+1,w  ; 
       andlw 0x04            ; Are we done? (We're done when bit2 of
       btfsc   STATUS,Z    ; the high order byte overflows to 1).
       goto     loop       ;                       
       goto     exit
eat5cycles
       goto     $+1         ; more wasted time to keep the loops even
       nop                      ; 
       goto     loop     ; 
exit
       movlw    0x06     ; set up for 2 analog comparators with common reference
       movwf    CMCON
ENDASM
RETURN

Green is on if there's movement(so values change) and yellow if there's none.