# Digital thermometer

Discussion in 'Electronics Homework Help' started by bilal, Sep 2, 2010.

1. ### bilal

6
0
Sep 2, 2010
I want to design a digital thermometer but without using MICRO CONTROLLERS PLZzZ HeLp

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
There are multiple circuits that will give you a linearly increasing voltage with temperature. Some of these can be connected directly to a digital panel meter to read directly in degrees C or F (or occasionally in K).

3. ### NickS

367
0
Apr 6, 2010
It looks like you fell asleep while trying to type please... are you ok?

Can you tell us what temperature range you need to monitor and in what type of environment? Also what kind of output display you expect to use. Without a micro controller it will need to be a pretty basic display.

4. ### bilal

6
0
Sep 2, 2010
well i want to measure human temperature in both C and F !!! and it ranges from 35C to 40C

5. ### NickS

367
0
Apr 6, 2010
Would that be human temperature on the skin or internal?

Have you considered using a thermocouple that interfaces directly into a DMM?

6. ### bilal

6
0
Sep 2, 2010
well i considered that even but i need accuracy and using DMM i am nt gttng that do u knw any other transducer that can work for me ??

7. ### NickS

367
0
Apr 6, 2010
0.025% accuracy is not good enough? --(based on claims for fluke 180 series)

So far we know that you want a simple circuit that measures body temp(98DEG F +/- 10 DEG?). It can not require use of a micro controller and it needs insane accuracy. Have I missed anything?

8. ### NickS

367
0
Apr 6, 2010
Here is an example of a linear thermistor type part MCP9700/MCP9701 and attached is a plot of the output voltage vs temp. Now you can make interpretation of the results slightly easier by gaining up the temp window you care about but your accuracy and resolution will still only be as good as the device you use to read it. Without use of a uC the results will likely be pretty course.

Good luck
-Nick-

File size:
30.9 KB
Views:
190
9. ### bilal

6
0
Sep 2, 2010
ok here simple it is i want to make a digital thermometer with a simple use of any transducer and then to display its value in seven segment display !! with the option of F and C !!!! nw PlZz help

10. ### NickS

367
0
Apr 6, 2010
You still here not told us what accuracy you need? But after you last post It does not really matter anymore.

I am all for going the pure analog route when it makes sense but you need a uC for this task. I personally think you don't stand a chance at switching between F/C on seven segment displays without using a uC.

11. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
Why not buy one of these?

12. ### bilal

6
0
Sep 2, 2010
well thats my project requirment to make a digital thermometer without using uC and to display its result in seven segment display !!!

13. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,501
2,841
Jan 21, 2010
In that case, it sounds like you want us to do your homework. Perhaps we can assist, but it's your project, not ours...

14. ### NickS

367
0
Apr 6, 2010
Good point Steve. If this project came from an instructor with those requirements then they are expecting some serious effort out of you to make it work.

If this project is your brain child and you chose the requirements, then I think you should re-evaluate your goals and come to terms with a more realistic approach. I am not aware of a simple circuit that does unit conversion math? I also have never seen a seven segment display used without a uC. Its just not a realistic approach to your end goal.

15. ### bilal

6
0
Sep 2, 2010
Thanks alot for your HELP !!!!!!