Reading an analog Thermometer that is in use (Op-Amp?)

Hey,

We have an old water temperature thermometer in the house, and I'm trying to log that temperature, while the normal box continues to use this thermometer.
It works very nicely with a multimeter, I can read the voltage and convert that to temperature.

However if I replace the multimeter with an analog input of a Intel Galileo the original reading drops and the galileo also doesn't get the correct temp.

I'm guessing the internal resistance of the galileo is not high enough? I tried a resistor in front of the input but if it is large enough to make a difference I can't get an good reading anymore.

From what I read on the internet a "non-inverted, linear op-amp" might be the answer, but is it?
And if so, which one should I get?
Most seem to need quite a high supply voltage?
If I would get a MCP6041 and connect the output to the inverted input, would that do the job?

Thank you very much for any help in advance.

Marvin

What kind of voltage is going through this "thermometer"

What else is connected to it?

The "temperature sensor" is connected with two wires to the controller box that uses this sensor.

The voltage seems to be 0-3.3V. At normal temperatures it is around 1.6V.

May bee what U need. Allows you read the voltage, without loading the circuit