I am trying to make a digital ohmmeter on a parallel port interface that can measure resistance with at least 95% accuracy. I have tried a 555 timer monostable assembly which generates a pulse with respect to the connected resistor. My program detects the width of pulse and then after calculation gives a value of resistance, but the results are not accurate, especially for small values. Is there any IC avaliable for resistance to digital converter? The output may be serial or parallel.
Electronic – Resistance to Digital converter
555adcmeasurementmicrocontrollerresistance
Related Solutions
Your scope is set to AC coupling.
I doubt that would be the case, Usually in a case like this the compiler would read the value of ADCRL and store it a location in memory that is associated with the variable val or proxval. You can verify this by looking at the generated assembly code by the compiler. But if your worried that's I would declare val and proxval as volatile variable. If val and proxval where pointers to ADCRL then yes calling one function would affect the other but as regular variable the value from ADCRL gets actually stored to variable
Related Topic
- Electronic – Simple measurment of resistance with microcontroller
- Resistance measurement problem with digital multimeter
- Electronic – Multiplexing of resistance measurements
- Electronic – Low resistance digital potentiometer – alternatives
- Electronic – Does multiplying range affect accuracy of an analog to digital converter
Best Answer
If you are familiar with microcontrollers then you can use an ADC. Place the unknown resistor as one half of a voltage divider (with known precision resistor), apply known voltage and measure the output at the junction. Do the math and you can work out the unknown resistance.
There are a few variations on this (see Wheatstone bridge, pictured below) and you can get quite complex with it the more accurate you need it to be (see LCR meters also - they use a known frequency and measure amplitude and phase angle, so you can obtain a lot more data, e.g. DF, Q, θ, etc)
Wheatstone bridge configuration:
You can also get ICs and off the shelf modules that can be configured to measure voltage/current/resistance/etc. Obviously a multimeter (e.g. with USB/RS232 link) will do what you are asking for, but I'm guessing there must be a reason you want to avoid this route.