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Topic: Arduino as a V-A multimeter (Read 10022 times) previous topic - next topic

Eric E.

#15
Mar 29, 2011, 05:57 pm Last Edit: Mar 29, 2011, 08:53 pm by Eric E. Reason: 1
My mistake - that would be an analog pin.

I'd like to test panels that generate anywhere from 0.1A to 6A, and eventually panels around 10A.

Morpheous

I have two working PCBs for the PSU. Now I'm trying to make LCDs which will display the voltage and the current. I'm going to use Arduino for measurment and voltage deviders. My question is, could I use only one Arduino board to measure voltage and current from both PCBs (because of the common ground, which I should use for the Arduino board)?

CrossRoads

Morpheus,
This thread has been all over the place, so I can't say.
If you are only measuring Voltages between Gnd & a positive level, then I would think you would want the Grounds of both boards connected together also to the arduino ground.
If you are measuring voltage across a shunt resistor like a floating multimeter, then you may not want to be connected to ground at all.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Morpheous


Morpheus,
This thread has been all over the place, so I can't say.
If you are only measuring Voltages between Gnd & a positive level, then I would think you would want the Grounds of both boards connected together also to the arduino ground.
If you are measuring voltage across a shunt resistor like a floating multimeter, then you may not want to be connected to ground at all.

I want to measure voltage and current, so I'll use a shunt resistor. But how I can measure like a floating multimeter, without connect the ground to the Arduino?

CrossRoads

When you use a multimeter, do you connect anything but the 2 leads?
Use the Arduino the same way.
Gnd to the lower voltage, and Analog in to the higher voltage.
DO NOT SWAP - Ground must always be lower, or you will damage the analog pin.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

capocchion

Hello everyone,
I'm a completely newbie about Ardunio but I find this discussion really interesting...

I'm working in a lab on a study about the corrosion of pipes and I want to build a data logger with Arduino.
Why? Because it's cheaper, smaller, more flexible (and more fun to do) than the data logger I'm using.

My measurement are just made with an electrode (reference electrode) every x second (i.e. every 5 seconds or 1 minute or whatever i set) then logged in a csv file. The measurement are mV.

The csv is really simple: Elapsed time - mV from Electr. 1 - mV from Electr. 2 - .... - mV from Electr. X.

something like this:



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Is it possible to do??? And how?? (like for example, to change the frequency of data logging).
Thanks :)

CrossRoads

What's the range of your signals?
Arduiono straight up has 10 bit ADC with 1 LSB limit of 5V/1024 or 1.1V/1024 if using the internal reference.
If you'l need better precision, then adding an external ADC will be needed.
A standard Uno type Arduino has 6 channels of analog going into a MUX for reading one at a time.

A 1284 based board has 2 more inputs, into the same mux.
A board like my "Bobuino" is 1284 based, also has and SD card for logging, and a Real Time Clock for recording the time of the samples with 1 second accuracy.
And you can add an ADCshield if you need more precision.

Writing the code to check for a minute passing, taking the 6-8 whatevever samples, and storing to the SD card would not be that difficult.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

capocchion

The range is more or less from -2 mV to +2 mV...

CrossRoads

You're going to need to amplify it then to use it with Arduino, gain of 1000 and some offset too, end up with 2V with no input, +/-2V from there.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

capocchion

I have no idea how to do and assemble the whole thing...

CrossRoads

Here's what you're after.
One input will be your signal, the other input will provide the DC offset.

You can do the equation in excel, makes it easy to adjust the resistors & play some, see what results you will get with standard resistor values.

http://masteringelectronicsdesign.com/how-to-derive-the-summing-amplifier-transfer-function/
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

capocchion

Thank you for your patience but I really don't understand anything about electronics...   :smiley-red:

I really need a step by step tutorial... Please...

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