After months of googling I'm starting to make sense on this until I found this page
where they state
The ADC is optimized for analog signals with an output impedance of approximately 10 k or less.
I'm using the ET-73 probes and have it wired up like this
http://hruska.us/tempmon/
I measured my thermistor with my DMM at about 220k at room temperature and have a 22k dividing resistor as shown on the link. Do I need to do something else with my circuit or am I ok?
Thanks
John
It should be OK, however as the impedance is higher it might need longer to settle down when swapping inputs. To do this take a reading of one analogue input, delay a few milliseconds and then take the reading again. Disregard the first reading and use the second one.
Thanks Mike. I assume that means if I read analog 1 then read analog 2 when I switch to analog 2 or back to analog 1 put in the delay.
John
Always do:-
read channel - delay - read channel and use results
for what ever channel you want to use.
While playing with some code to directly control mux channel selection I found that a delay(50), 50millisec, was a good value to get a stable and accurate reading after selecting a different channel.
Lefty
Yes but it does depend on the impedance of the voltage source you are measuring.
Yes but it does depend on the impedance of the voltage source you are measuring.
Yes, fact. I was reading the internal bandgap voltage.
Lefty