New to Thermistor Sensor Help

I posted this in the project help section then realize that it was probably more applicable to this board. So sorry for first post.

A friend of mine gave me a couple of thermistors to play around with and I’ve never used them. I’m having a bit of trouble and am hoping someone could help me out.

First problem: The thermistors are a 5k ohm and a 2.2k ohm thermistor. I have a 5.1k ohm resistor to pair with the first, a proper 2.2k ohm resistor for the 2nd. Is not having a precise pairing an insurmountable problem?

Second: Neither thermistor has a data sheet that includes the constants for the steinhart equation which seems to be the go-to route for computing temp. Is there a way for me to figure out the constants from the information provided in the data sheet?

Third: All of the Arduino tutorials on thermistors use a 10k ohm thermistor. Why is that?

I know that I could make a fairly accurate guess at temp using the data tables provided in the data sheets with the two thermistors but I’m concerned about memory in the program I’m inserting this into. It’s a fairly long and complex oven control system and memory is somewhat of a concern.

The thermistors I was given are:
2.2k Ohm thermistor:http://www.newark.com/jsp/search/productdetail.jsp?SKU=21C9790
5k Ohm thermistor:http://www.newark.com/jsp/search/productdetail.jsp?SKU=86R9240

The data sheets are accessible through the Newark pages if you want to take a peek.

A huge thank you for any help you can offer.

You can compute the constants for your thermistor given three sets of resistance/temperature pairs. There are web calculators to do the math.

The fixed resistor in the voltage divider does not have to match the nominal (25°C) resistance of the thermistor. Measuring the resistance is the important thing. Knowing one of the resistors and the voltage across the resistor you can calculate the resistance of the other resistor. As long as the fixed resistor is well under 100k it should work fine.