Hello all
Does using analog multiplexing require any particular considertaions to be taken care of?
I have a circuit with a 12 bit ADC,ADS1286.The input is in mV(steady inputs right now), which is fed to the ADC through an amplifier(gain=100).Using 16f877a.
Now all was fine(variation of +/-1 LSB) when the input was directly connected to the amplifier.
Sometime back,I put a multiplexer (cd4097),to make it multi channel.(change of channel every second).After which,the readings have been going beserk(variation of around 20,no specific pattern).
Tried keeping the multiplexer channel steady,.i.e.gave the input to just 1 channel,read once per second.No effect.
This is the code I am using to slect the multiplexer channel
So,I would like to know whether there are any particular issues regarding analog multiplexing,taht ahould be considered,and I have missed??
Thanks.
Does using analog multiplexing require any particular considertaions to be taken care of?
I have a circuit with a 12 bit ADC,ADS1286.The input is in mV(steady inputs right now), which is fed to the ADC through an amplifier(gain=100).Using 16f877a.
Now all was fine(variation of +/-1 LSB) when the input was directly connected to the amplifier.
Sometime back,I put a multiplexer (cd4097),to make it multi channel.(change of channel every second).After which,the readings have been going beserk(variation of around 20,no specific pattern).
Tried keeping the multiplexer channel steady,.i.e.gave the input to just 1 channel,read once per second.No effect.
This is the code I am using to slect the multiplexer channel
Code:
;PORTE connected to channel select pins A,B,C of 4097
;spi_interface_port=PORTC
;RC0 connected to INH of 4097
clrf PORTE
banksel TRISE
clrf TRISE ;set PORTE as output
clrf STATUS
bcf spi_interface_port,bit0;get the INH pin low to enable the chip
nop ;settling time
nop
movlw b'00000001';select channel 1
movwf PORTE
nop;settling time
nop
So,I would like to know whether there are any particular issues regarding analog multiplexing,taht ahould be considered,and I have missed??
Thanks.