making ohmmeter

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hi
i decided to make a ohmeter with avr and i try "Getrc" in bascom but it dosent work well how can i do it in best way???

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How often do you plan to ask the same question?

Stealing Proteus doesn't make you an engineer.

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DId the bascom project come with a file that explains the "best way"?

If not then it is your responsibility to troubleshoot your circuit.

Jim

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Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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As you seem to be new at this, have you cleaned the board of all traces of contaminants eg. solder flux residue? These create leakage and will play havoc with your readings. IsoPropyl Alcohol is recommended.

Also, read up on board/surface leakage currents and ways of minimising them. These shouldn't matter so much on the lower ranges, but are crucial when measuring high resistances.

If you think education is expensive, try ignorance.

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What is your intent ?

Obviously, you could go buy an ohmmeter. But since you are wanting to build one with an AVR, I assume that your intent is to learn.

As with any project, you need to have a plan, or at least some expectations of what you are trying to do. Of course, plans often change as you encounter problems. Some things to consider for your ohmmeter project are:
1. Range(s). If multiple ranges how do you select ?
2. Accuracy ?
3. Display Type ? LCD, 7 Segment, etc
4. Use internal A/D or external ?
4a. Display resolution ?
5. Method ? Current source or resistive divider.

Items 4 and 4a are related. With the 10 bit internal A/D your ohmmeter is limited to 1023 "counts". This means your displayed values and ranges might look something like this.

1 ohm resolution 0-1023 ohms
10 ohm resolution, 0-10.23K
100 ohm resolution 0-102.3K
1000 ohm resolution 0-1.023MEG

Of course, if you had an external 12 bit A/D, your ranges would be different.

Come up with a plan and let everyone know. I'm sure that we will be able to provide help for specific problems as they arise.

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Bascom's "GetRC" is not intended for accurate measurements .... it's for indication purposes only. And that is explained in the Help-file.

Nard

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Having once been on a multimeter production line (about a quarter of a century ago), I'd like to point out that the quality of components and the PCB itself is critical. You will not believe the number of capacitor manufacturers we evaluated (and rejected) for leakage and other parameters. :( Thank heavens manufacturing techniques have improved greatly since those days, but resist the urge to buy unbranded components for this project.

India is very humid; lots of rain. We found in one case that PCBs cut from the edges of the huge blanks (copper clad sheets) gave more leakage. Apparently moisture was creeping into the epoxy from the exposed cut edges, creating leakage paths that necessitated the baking of the blank PCBs in an oven to get rid of the moisture.

If you think education is expensive, try ignorance.

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hi thank you all i really want to make an ohmmeter but i dont know should i use a/d or voltage & current i want some thing that have loest mistake.