Accuracy of analog sensors in Arduino Uno?

Using Arduino Sensors
1

I'am trying to read out an analog BBQ temperature sensor as described in this thread.

The problem is that I'm getting fluctuating adc values from the analog pin very often. (+- 6 steps) That means a difference of up to 5 degrees celsius every time which is not accurate enough for my project. I measured the voltage from the temperature sensor with a voltmeter and the voltage is much more constant than what I'am getting back from the adc sensor.

Are the analog sensors of the Uno simply not accurate enough or am I doing something wrong here?

2

TheNetStriker:
am I doing something wrong here?

Definitely: you fail to provide any information that could be useful to help us help you.
What sensor?
How is it installed?
How is it connected?
With what type of wires?
What's the rest of the circuit?
Let's start with that.

3

wvmarle:
Definitely: you fail to provide any information that could be useful to help us help you.
What sensor?
How is it installed?
How is it connected?
With what type of wires?
What's the rest of the circuit?
Let's start with that.

It is all described in the thread I mentioned. I use the same sensor as in the thread and I'am connecting it the same way and also with a mono jack adapter. At the moment everything is on a protoboard, but I don't think that this is the problem. I measured the voltage directly on the proto board and there it is constant.

The only difference to the project is that I also attached this lcd: Play-Zone.CH LCD Keypad Shield für alle Arduino

Any ideas what could be the problem?

4

Did you use a 10K or 100K sensor?
Which resistor did you use?
How long are the wires to the probe? Are the wires twisted pair?
Did you solder the connections?
Are all the grounds connected?

5

How do you measure that voltage?
6 ADC points is just 30 mV change. Most multimeters will average that out if it's a short peak.

6

jremington:
Did you use a 10K or 100K sensor?
Which resistor did you use?
How long are the wires to the probe? Are the wires twisted pair?
Did you solder the connections?
Are all the grounds connected?

Thanks for the reply. I'am using a 10K fixed resistor. The wire to the probe is only 10 cm long and not twisted. Only the wires on the lcd board are soldered at the moment, the rest is just plugged into the proto board.

I've now measured the voltage using an oscilloscope and with that I could measure the voltage differences. I will try if soldering all connections solve this problem.

7

Soldering every connection did help. The temperature reading is now stable! Thanks for the hint!