[solved] Current temperature value

[shady79]

Hello

Can anyone explain me one thing.
I have some ds18b20 sensors and cacti draw charts for them.
I get current temp. from sensor using python script.
I noticed that current temp in graph is a little overestimated compared to actual value. Sometimes the difference is about one degree.
In graph template item for current temp is set like that:


regards
shady

[BSOD2600]

Sounds like rrdtool consolidating data over time. read up http://docs.cacti.net/manual:088:8_rrdtool

[shady79]

Thanks for replay.
I still have a problem with current value of temperature when it falls below 1



It is represented as 630.00 instead of 0.63
When I exported some data to csv file - values are as follows:

2015-01-08 17:50:00 1.0683333333e+00
2015-01-08 17:55:00 1.1861000000e+00
2015-01-08 18:00:00 1.1312000000e+00
2015-01-08 18:05:00 1.0614000000e+00
2015-01-08 18:10:00 1.0018000000e+00
2015-01-08 18:15:00 8.8240000000e-01
2015-01-08 18:20:00 8.8000000000e-01
2015-01-08 18:25:00 9.3880000000e-01
2015-01-08 18:30:00 8.1216666667e-01

Maybe I must tweak some settings in cacti but I have no idea where...

Regards
Shady

[shady79]

My script that gets the temperature..

Code: Select all

import os, glob, sys
#import rrdtool
from time import sleep

# Load the 1-wire modules (if modules are loaded on boot these two lines can be commented out)
os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

# Set up some variables
base_dir = '/sys/bus/w1/devices/'
devices = glob.glob(base_dir + '28*')
device_file = '/w1_slave'

def read_temp_file(device_file):
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines

def read(id):
        device_dir = '/sys/bus/w1/devices/'+ id + device_file
        raw_data = read_temp_file(device_dir)
        while raw_data[0].find('YES') == -1:
            sleep(0.1)
            raw_data = read_temp_file(device_dir)

        t_pos = raw_data[1].find('t=')

        if t_pos != -1:
                temp = float(raw_data[1][t_pos+2:]) / 1000
                temp = round(temp,2)
                print temp
                # return temp



try:
        read('28-0000051eb082')

except KeyboardInterrupt:
    # quit
    print('Exiting application')
    sys.exit()

Maybe here is a problem...

[phalek]

This falls into this FAQ entry: http://docs.cacti.net/faq#show_exact_numbers

[shady79]

This falls into this FAQ entry: http://docs.cacti.net/faq#show_exact_numbers

Thanks that's it