Design of Analog Temperature sensor

i wanna ask about if there is any idea about how to design analog temperature sensor null type and the types of components needed to implement the circuit of the sensor

thanks in advance,

i wanna ask about if there is any idea about how to design analog temperature sensor null type and the types of components needed to implement the circuit of the sensor

thanks in advance,

Look for Arduino+TMP36 ...

Do you really mean you want to 'design your own', or are just looking for a solution? Texas Instruments produce many very easy to use analog temp sensors like the LM35, LM45, LM60 etc that cost next to nothing.

If you wish to do it with just basic passive components, simply set up a voltage divider using an NTC or PTC thermistor - a resistor whose value changes with temperature, with either a negative or positive temperature coefficient. However, you will not achieve the same level of accuracy with such a simple solution. Plus, precision NTCs/PTCs are probably nearing the price of a temp sensor IC anyway...

Hope that helps!

Not sure what you mean by Null type.

Are you asking if there is an analog temperature sensor you can use with the arduino? See above
If you are asking how do I make my own analog temperature sensor, this is not really the best place for that, though I would look at RTDs, thermocouples and possibly look for diodes that respond to temperature. RTDs are the usual method.

Please do not cross-post. This wastes time and resources as people attempt to answer your question on multiple threads.

Threads merged.

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what is the best resistance for thermistor , measuring temp. 0-100degree, with arduino 5v?

mortenx:
what is the best resistance for thermistor , measuring temp. 0-100degree, with arduino 5v?

Depends on the Thermistor. I would find one that will go beyond 0-100 (You should always include units), then create a voltage divider, and use the second resistor as something that is near the center resistance of your range. This should give you a good range of voltages to measure with.

can i power up thermistor with digital pin for preventing thermistor to all time powered and self heating?

mortenx:
can i power up thermistor with digital pin for preventing thermistor to all time powered and self heating?

So long as you don't overload the pin (40mA is the absolute maximum, in practice you
would limit to 25 or so). Note that output pins have about 30 to 40 ohms on-resistance
that may be quite sensitive to temperature (some experimentation might be needed to
quantify that), and will vary from device to device too... That would suggest a high resistance
for the thermistor. Alternatively you could use an external MOSFET (logic level) to switch
the thermistor circuit, and such MOSFETs can have negligible on-resistance (0.01 ohms!).

The fixed resistor should be a 1% type with low tempco (temperature coefficient) to
reduce errors from ambient temperature.

The other aspect is thermal design of the probe itself - what are you wanting to measure?
Remember temp sensors pick up radiated heat as well as conducted heat and in air
the radiated component may not be negligible. In liquids or forced air-flow the conduction
is much better and will dominate. A metal probe is usually much less affected by heat
radiation (IR) than other materials. (For instance the DS18B20 sensor in black epoxy TO92
package is affected by this).

i want to measure composting process its about 10-70 degree C.. i am thinking ... what sensors are the best solution fot that..
thermocouples, thermistors or ds1820...

If you're using the unregulated output of the digital pin to supply the voltage, why bother with a 1% resistor?

The advantage of the DS18B20 is that the signals along the wire are digital. As long as you can read them, the length does not matter. The long wires might affect a fhermocouple of thermistor measurement. Another clever way is to create a little self contained wireless sensor, but you need to change the batteries every so often.

but ds1820 network is very weak.. if one sensor gets wet or signal is interrupted then whole 1wire network gest messy..
plan is to measure 30-40 temp points.. lots of wires and lots of things that can go bad, because composting process can be very acid and destroy wires and isolation..
i mean that when thermistor is broken it is not affect others in system..

DS18B20 is not "weak" or any weaker than any other type of network. Also, acid/corrosion/mice/backhoes can destroy any type of sensor network.

A network of either thermistors or thermocouples is still going to require an analog to digital conversion for the network -- you can't send analog signals long distances and expect any accuracy. The benefit of the DS18B20 is that it wraps all of that up into one little, 3 pin package. You're not going to be able to beat it.