Measuring resistance of thermistor in potential dividers

1. Apr 5, 2009

lefty989

Hi there, first off I hope this is ok to post here. Quite a simple question.
I have done an experiment simply to work out the resistance of a thermistor at different temperatures, I did a prelim with a simple circuit of just ohm meter + thermistor. Then I did the main one with a potential divider circuit.

1. What is the advantage of using a potential divider circuit over a simple one to measure resistance of a thermistor? (Read above)

Thanks for any replies. I'm a bit unsure as to why it would be better. :-/

2. Apr 5, 2009

OmCheeto

What were the currents flowing through the thermistor in two different circuits?
You can calculate this by getting a voltmeter and measuring the voltage output of your ohmmeter.

My voltmeter measures 3.051 vdc from my ohmmeter on the 2k ohm scale.

3. Apr 5, 2009

lefty989

Why is this necessary? I just need to know what makes this circuit a better way to do it.

But the current at say 20degrees was about 0.4 set at 20mA for potential divider. I didn't check the current for the other circuit. just had a resistance meter and thermistor.

4. Apr 6, 2009

OmCheeto

Because it points you to the answer.
You need to know how much current is flowing through the thermistor in each of the circuits, and how that current affects your readings. Are you familiar with the equations:
P = IE = I2R = V2/R

And how does P manifest itself in a purely resistive circuit?

And how does that affect R of the thermistor?

And how does that affect your measurements?

5. Apr 7, 2009

lefty989

Right... Thanks for the help..

Im not really understanding what you mean by the first question.
Yes I do know the equations.

6. Apr 7, 2009

Redbelly98

Staff Emeritus
(Excuse me for jumping in.)

I think OmCheeto is asking, what happens to the electrical energy when current flows through a resistor? (Hint: it gets transformed from electrical energy into ____ energy.)

7. Apr 8, 2009

lefty989

Ahh ok. Hope Im right in saying heat energy? So a guess, does this mean the heat will affect the resistance output from the thermistor? That makes sense, so you use a potential divider circuit to eliminate that problem?
I am not quite sure why... (Is it something to do with the other resistor in series?)