Measuring AC Voltage

[hamsiii]

Hello all, I want to measure AC voltage from mains electrical cables, 100-220V AC voltages.
For this measurement, I will use I/O pins of a microcontroller or an ADC. So the measurement will be around 0-5V.(or 0-3V) Besides, I do not need any LCD panel to show the data, as the data will be sent to another microcontroller to be processed.
Do I need only a voltage divider or a DC/DC converter to convert 220V to 5V? I am not in favor of converters as the circuit should be compact to fit in the circuit box.
For current measurement, there are current sensors but no voltage sensors for voltage measurement. I only need a circuit to measure 0-220V like voltmeter and without the LCD panel.
I also need an accuracy of %1 maximum. Do you have any recommendations?
Thanks in advance.

 

[Reloadron]

If you want a 1% uncertainty I would think about a commercial voltage transducer solution along these lines. The link being just an example as transducers like this are marketed by plenty of companies. They also come in true RMS versions if that is what you need or want.

Ron

 

[alec_t]

Importantly, for safety's sake you should have some way of providing isolation between the mains and the micro.

 

[hamsiii]

thanks for the replies however, i need a smaller component than these transducers. Is there an IC for this purpose? My last chance would be transducers in this case.

 

[Reloadron]

I do not know of anything smaller that will do what you want. Sorry.

Ron

 

[ronv]

I wonder if you could use a small transformer and calibrate its output.

 

[hamsiii]

i thought of a transformer, however there is already a transformer for voltage supply in the circuit. So, there should not be any more transformers. Instead, I thought of an IC that measures voltage. Unfortunately, there are just small voltage measuring IC's that I could find.

 

[alec_t]

however there is already a transformer for voltage supply in the circuit.

Can you use the secondary voltage of that to measure (knowing the transformer in/out voltage ratio, which may have to be determined by calibration) the mains voltage indirectly?

So, there should not be any more transformers.

Because of limited space?

 

[hamsiii]

Hi Alec, I can use the secondary voltage for just one phase of the AC voltage cable. However, I have three phase AC voltage, so there could not be 3 transformers to be calculated. And, yes there is limited space.

 

[alec_t]

However, I have three phase AC voltage

It would have been nice to know that at the start

 

[ccurtis]

For current measurement, there are current sensors but no voltage sensors for voltage measurement.

Those current sense ICs provide isolation, and I would suggest selecting known value resistors and a current sense IC for each phase to measure each line current, then convert to voltage by computation.

 

[Reloadron]

If this is poly phase as you later stated everything is changed. Three phase wye or delta (3 or 4 wire 3 phase)? The only way to go about this is using a transducer made for the application. You also fail to mention if you want true RMS voltage measurements. There is no way you will do this with something tiny or real small.

Ron

 

[Muhammad Hassan Akhtar]

I need to measure 220 V and currents around 13 Amperes using PIC micro-controller. The circuit I have designed on Proteus using differential amplifier that converts 220 Volts to 2.5 volts (0-5 volts range) taking 40 samples of the peak voltage is given below. The ADC of PIC is used for converting analog voltages into digital. The voltage divider divides the voltages into half so that it comes in the range of (0-5 volts) which can be read by PIC. It's showing the values of voltage and current on the input side accurately on LCD but I have some confusions regarding this circuit.
1. First of all is this circuit okay as I have some doubts about it?
2. Should I use a current transformer and voltage transformer on the input side?
3. The 1 ohm bypass resistor should be used if I use a current transformer or should I use only high power wire wound resistor only instead of CT for current measurement?
(I'm a student so I don't have much experience in this area. So kindly explain everything)

 

[tvtech]

Welcome to ETO Muhammad

You do realize this thread is Two years old...

Better to start a new Thread rather.

Regards,
tvtech