How low Vref can a PIC use without sacrificing accuracy? Wich method should I use to read a signal from ex. LM35, wich give 10mV pr. deg. Celsius --> approx. 250 mV for room temperature.
Generally, to convert a low voltage signal, should I attenuate the reference, or should I amplify the signal?
At the moment I'm using a 16F684 reading a LM35, with just a normal diode as a 0,7 V reference to the Vref pin. Displaying the result on a LCD. No particulary project really, just fiddling on the lab to learn more.
I have two different voltage reference circuits at hand; TL431 and LM385-2,5 . Both giving 2,5 V reference. I'm thinking of dividing the voltage with two resistors, then feeding the Vref pin. Are there any max/min values for the resistors I should be aware of? Any minimum impedance for the Vref, as for the A/D input?
Btw. How do I get the degree character on the LCD? The "little o" in degrees Celsius.
Generally, to convert a low voltage signal, should I attenuate the reference, or should I amplify the signal?
At the moment I'm using a 16F684 reading a LM35, with just a normal diode as a 0,7 V reference to the Vref pin. Displaying the result on a LCD. No particulary project really, just fiddling on the lab to learn more.
I have two different voltage reference circuits at hand; TL431 and LM385-2,5 . Both giving 2,5 V reference. I'm thinking of dividing the voltage with two resistors, then feeding the Vref pin. Are there any max/min values for the resistors I should be aware of? Any minimum impedance for the Vref, as for the A/D input?
Btw. How do I get the degree character on the LCD? The "little o" in degrees Celsius.