History of AfreshTiny/AnalogInput
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2015-01-01 07:00:00 . . . . MembersPage/MarcellGal [analog input notes]
2015-01-01 07:00:00 . . . . kozpont.realszisztema.hu [Analog input reference voltage problem]
2008-04-08 20:16:20 . . . . MembersPage/MarcellGal [button threshold]
2008-02-13 16:23:19 . . . . MembersPage/MarcellGal [Round Analog input display and logging]
2007-09-24 17:32:39 . . . . MembersPage/MarcellGal [analog input offset]


Changes by last author:

Changed:
Problem with using linear output transducers
Using high output impedance transducers with round devices manufactured before 2008-10
Changed:
Using the analog input with MAP sensor makes some problem as we discussed on the vems.co.uk forum [1]with Rob. He adviced me to write here my observations.

I used an OE Marelli map sensor ( pdf datasheet is [2] ), measured the applied pressure, map sensor output signal and megatune raw value (linear curve, calibration is 255, offsett is 0)

Using the analog input with OE Marelli MAP sensor makes some problem as we discussed on the vems.co.uk forum [3]with Rob. He adviced me to write here my observations.

I used an OE Marelli map sensor ( pdf datasheet is [4] ), measured the applied pressure, MAP sensor output signal and megatune raw value (linear curve, calibration is 255, offsett is 0)

Changed:
The positive range is nearly linear, but the vacuum is unusable. The sensor can't pull the signal below 2400 mV, so unable to measure below athmospheric pressure. (without connected signal line the map sensor out is working properly of course).
The positive range is nearly linear, but the vacuum is unusable. The sensor can't pull the signal below 2400 mV. Even than it is able to measure below athmospheric pressure, just compensate with the 17 point curve. (without connected signal line the map sensor out is working properly of course).
Changed:
disconnected analog in (4v) megatune shows 1520

pull the ground (0V) shows 1040

pull up to 5V shows 1600

There is a breakpoint at 4V. Unfortunatelly I didn't have a variable resistor at hand to do more measuring point.

I think the reference voltage on the gauge input makes problem to use the analog input correctly.

* disconnected analog in (4v) megatune shows 1520

* pull the ground (0V) shows 1040

* pull up to 5V shows 1600

Calibrate the 17 point curve so it shows 0 where you like (eg. when connecting ground). That's all.

The input impedance of round devices since 2008-10 have much higher input impedance (around 40 kOhm). Therefore it is easier to use with high output impedance transducers. Recommended operation modes:

* leave analog input pin open (not connecting signal)

** button_threshold=175 (not 128 as the dialog in older megatune round.ini suggests)

* connect signal to analog input through 0..10kOhm resistor

** disable button (button_threshold=0)

* connect signal to analog input through a higher resistance series resistor (around 100k)

** it becomes important to change the 17 point curve for proper calibration

** set suitable button_threshold if it is intended to use the button