i am trying to use an input on the k8055 as a voltmeter. im measuring 12v sealed lead acid batteries which have a usage range between 12.2 volts and 14.4 volts.
to maximise the accuracy i am using a 12 volt regulator with another battery (fully charged). i attach the ground for the input of the k8055 to the output of the regulator and the a1 connection to the + of the battery i am measuring. since the regulators output is measured at 11.51 volts the measured range is from 11.51v-14v (0-2.5v after the regulator, and using a multiplier of x2 on the k8055). this means i get about .01 volts per bit.
now in my software i calibrate a linear equation to the bottom and top of this range which seems to work fine. but when i check it again a day later my results are all out by .05 volts which is bad news.
i have a feeling this may be the regulator changing due to different temperatures or something like that, but im wondering if there are any other ideas people have here to get accurate measurement (down to .01 volts with a 12.2-14.4 volt variable range). thanks if you have any ideas.
after doing some further testing it appears to be the regulator is the cause of the problem. is it possible to find lower tolerance type regulators for accurate measurement or perhaps a circuit of different design that will suit my purposes?
[quote]is it possible to find lower tolerance type regulators [/quote]Indeed, it is.
In Google type in: “voltage reference” 10V
Here the first result as an example: 10V Precision Voltage Reference: focus.ti.com/lit/ds/symlink/ref102.pdf
Maybe too good to use with the K8055 !
FEATURES
+10V ±0.0025V OUTPUT
VERY LOW DRIFT: 2.5ppm/°C max
EXCELLENT STABILITY:
5ppm/1000hr typ
EXCELLENT LINE REGULATION:
1ppm/V max
EXCELLENT LOAD REGULATION:
10ppm/mA max
LOW NOISE: 5μVPP typ, 0.1Hz to 10Hz
WIDE SUPPLY RANGE: 11.4VDC to 36VDC
theres another problem with that one, its only available as surface mount and im not sure how it will work in combination with another reference.
do any 12v (or higher with a trim) references exist? i want to keep it to one package if possible. i haven’t had any luck finding them. thanks for the help guys.