mohon bantuannya

[winda]

assalmualaikum..

mohon bantuannya, saya baru dalam menggunakan labview dan arduino.. saat ini saya sedang mencoba buat sistem monitoring aliran daya.. saya terkendala untuk menghitung nilai frekuensi dan beda phasa.. ini yg pernah saya cobaa,, tpi malah error.. mohon koreksi dan arahannya

[Nathan_B.]

What are the range of freqencies that you are expecting to experience in your system?

Specifically about your VI, you have wired a front panel value to the signals input on the express VI.  This is not correct.  That input is expecting an array of data to be processed.  It would probably be better if you described thd system that you are measuring and what values you need to obtain.

[winda]

I made ​​a flow monitoring system for solar cell power,, which previously has been used an inverter to convert it into an AC signal .. I use current and voltage sensors to read current and voltage values​​, then the output of the sensor input to the Voltage adder, adder's output   will be input to the arduino. and will read the voltage and current values ​​and calculate the frequency of the system and the phase of the voltage and current ..

sir please help me, because I am new to using arduino and labview ..

thanks before

[barddya]

Winda,

If you are beginning to use both Labview and Arduino, I would suggest to go straight to LINX

https://www.labviewhacker.com/doku.php?id=lvh_blog:user:sammy_k:2014_07_10_lvh_xbone

Also look at working examples, and modify a working VI to your specific design.

Regards,

Barddya

[Nathan_B.]

In addition to the suggestion to using LINX, I would recommend that you first look a the fastest rates that can be achieved.  Assuming that you are talking about standard US AC electricity (60Hz), you would need to be able to sample at least at 120Hz (See:  Nyquist Theorem) but it would be even better if you could sample much faster.

So, look at the documentation to make sure that the Arduino/LabVIEW solution is even a viable solution (I have not done the math).  You can also try to look into the "continuous acquisition" with the Arduino but you would probably need to take snapshots and process them (take a sample and then stop and then process that sample), then repeat.

[hrh1818]

AC Amplitude Measurement

There a couple of approaches that can be used to measure AC Voltages with Arduino and are compatible with LIFA.   One could use a precision AC Rectifier. See

<http://www.simplecircuitdiagram.com/2010/05/07/the-full-wave-rectifier-and-averaging-filter/>

The other approach is collect many samples of the signal and calculate the RMS value.  However, because Arduino's 0 to 5 volt DC analog to digital converter input range is incompatible with a plus and minus going AC signal an op amp is required to offset the AC Signal.  Next collect approximately 1000 samples of the signal using continuous sampling and calculate the average value of the samples.  The average value is equivalent to the 0 volt reference for the AC signal with out offset.

Next an integer multiple of cycles of the signal is required to calculate the RMS value.  I suggest using the following method to find the zero crossing points of the signal before an offset is added to the signal.   First find the first three consecutive samples greater than the average value.  The index for the first value in the set of three is the first zero crossing point.   Second using the first zero crossing as starting point find the first three consecutive samples less than the average value.  The index for the first value in the set of three is the second a  zero crossing point.  Third using the second zero crossing value as starting point find the next three consecutive samples greater than the average value.  The index for the first value in the set of three is the third zero crossing point.  

The difference between the indexes for the third and first zero crossing point is the number of samples in one cycle.  Next on could use an integer multiple of the number of samples per cycle when calculating the RMS value or continue looking for zero crossing points.   When calculating the square of a value one needs to determine the difference between an analog reading and the average value before performing the squaring operation.

Frequency Measurement

I suggest using the frequency measurement software and the circuit from this site to measure the frequency of the AC signals.

<https://www.pjrc.com/teensy/td_libs_FreqMeasure.html>

This frequency measurement software is not compatible with LIFA or LINX.

Phase Difference Measurement.

I haven't found a way for making phase difference measurements with Arduino Uno boards.

However, I did find this Arduino Shield for measuring

• Apparent Power, Real Power*, Power Factor* and AC RMS voltage readings*

<http://shop.openenergymonitor.com/emontx-arduino-shield-v2-smt/>

Plus the following two sensors.

<http://shop.openenergymonitor.com/100a-max-clip-on-current-sensor-ct/>

<http://shop.openenergymonitor.com/ac-ac-power-supply-adapter-ac-voltage-sensor-us-plug/>

A voltage sensor is required for Real Power*, Power Factor* and AC RMS voltage readings*
Total cost is about US$70.00 with insured shipping and tracking.

hrh1818