Measuring Resistance 0 -100 Ohm 1

[kchaloup]

I'm trying to design a circuit to measure a resistive probe which has a range from 0 - 90 ohms and provide a linear readout via LEDs. Any suggestions?

 

[Lewish]

Do you want a bunch of single round LEDs in a row, or do you want 7-segment LED readout?

 

[nbucska]

What is the range and accuracy? ( at 0 ohm you must have
absolute error, not % !)
<nbucska@pcperipherals.com>

 

[kchaloup]

There will probably beten LEDs. Also, a couple of trip points for alarm conditions.

 

[melone]

What is this for? Perhaps it might be easier to buy something that is already available?

 

[kchaloup]

I'm interfacing to a resistive fuel probe. The probe varies from 0-90 Ohms depending on how much of the rod is in contact with the fuel.

 

[algarin]

Hi, can you tell me what values wants to read in the display ?

if you want a reading from 0 to 100 with how many decimals ?

 

[kchaloup]

Actually,

I really don't want numeric display. It will just be a row of 10 LEDS.

 

[nbucska]

Simplest solution is to use a microcontroller with an on-board ADC. It can be less than $10.- <nbucska@pcperipherals.com>

 

[carnage]

how about a four bit ADC and a 4 to 16 demultiplex. set up your range to not use values B-F and you have ten led's plus one value for none of them being lit.
seems simpler than a microcontroller to me, but I prefer solder to software.

 

[biomedicalEng]

there is an IC that provides everything you want!

national semiconductor's LM3915:

The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, LCDs or vacuum fluorescent displays, providing a logarithmic 3 dB/step analog display. One pin changes the display from a bar graph to a moving dot display. LED current drive is regulated and programmable, eliminating the need for current limiting resistors. The whole display system can operate from a single supply as low as 3V or as high as 25V.

wow!!!!

isn't it what you desire everyday?

my friends call me the IC MASTER 2002!!!

do u think it's right?

lol

ok now go and enjoy from this IC.

here is it's datasheet:

http://www.national.com/ds/LM/LM3915.pdf