[QUOTE=richard;157122]define tolerance its not a general parameter for pot ratings, resistance should not be relevant... [/[QUOTE]

I meant would a 1K or 2K pot be "generally" better for ADC on a 16F18855.


[QUOTE]...Resistance:
The total resistance of the potentiometer, measured from one terminal to the other... [/[QUOTE]

5K, linear


[QUOTE]...Rated power :
The maximum amount of power the potentiometer can handle without overheating or failing...[/[QUOTE]

Rated power: 0.05W
Switch rated power: 12 VDC at 1.0A max


[QUOTE]...Resolution :
The accuracy of the potentiometer's resistance changes
Expressed as a percentage of the total resistance...[/[QUOTE]

I don't see this spec in the datasheet


[QUOTE]...Temperature coefficient :
How the resistance of the potentiometer changes with temperature...[/[QUOTE]

20℃-75℃:△R/R≤±5%
-25℃-20℃:△R/R≤±4.5%


[QUOTE]...Mechanical life:
The expected lifespan of the potentiometer
Usually expressed as the number of cycles it can endure...[/[QUOTE]

10,000 Cycles min.


[QUOTE]...Taper :
The relationship between the mechanical position and resistance ratio
The most common types are linear and logarithmic...[/[QUOTE]

Linear, (1B);B1 on Bourns pot specs


[QUOTE]...what is a weak pot...[/[QUOTE]

A noisy piece of crap that doesn't go anywhere near the full range of 0-5000ohms.


[QUOTE]...only that acquisition time is lower, a 10k pot could have 10 ohm resolution
in order to have "stable" 10bit result from a 10 bit ADC you would need 16 times over sampling.

to begin with you would need 16 times over sampling or use a 12 bit adc.
are you using 10 turn pots?...[/[QUOTE]

1 turn, 300 degrees


[QUOTE]...i cannot see how 0.25 degree resolution is useful for a 270 degree pot, most humans would be lucky to move it accurately in 2.00 degree increments

how is that going to work if the pots are not all identical, i have not encountered a pot that has a wiper that doesn't read 0 ohms to an end terminals at extreme rotation on my multimeter low ohms scale. how badly off are these pots . it would be easier to get better stock...[/[QUOTE]

I'm solo in this venture, so money is not unlimited, unfortunately.


...in c i usually use a map function to get desired result range from an expected input range, about 1000 times easier and vastly more flexible than any hardware solution

int16_t map(int16_t x, int16_t in_min, int16_t in_max, int16_t out_min, int16_t out_max)
{
return (long) (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}
1. I could have a QC test and fail any pot below a certain spec.

2. I could add code to calibrate each pot after assembly, and store a "conversion formula" in memory.

3. I'm hoping a combination of:

- raising VREF- to 0.5V,
- FVRx4,
- Henrik's idea in previous post can produce acceptable results.


There's only so much you can do on a limited budget.