230Vac sensing using AMC1100

Senthil Prakash Jayaprakash

Other Parts Discussed in Thread: AMC1100

I would like to design a voltage bus monitor for 230Vac, 50Hz. Variation expected on mains voltage is +/- 25% and negligible variation on frequency. I have referred the application report SLAA552 in which Fig 5. clearly shows the circuit for monitoring the instantaneous voltage. I require RMS voltage to be measured and not the instantaneous voltage. It is also fine If I can get the peak voltage, so that RMS can be calculated.

I have tried using bridge rectifier and a buffer capacitor between Line and R10 resistor in Fig 5. of application report SLAA552. But simulations are not convincing.

Please suggest circuit using AMC1100 to measure the input RMS.

Thanks and Regards

Senthil

over 12 years ago

0 Jose Duenas over 12 years ago

TI__Genius 9975 points

Hello Senthil,

Are you interested in performing a true RMS voltage measurement that reports an output analog signal or are you interested in a circuit that detects the peak voltage and scales it?

If the AC peak amplitude where to change, how fast do you need the RMS measurement to be updated?

Best regards,

Jose

0 Senthil Prakash Jayaprakash over 12 years ago in reply to Jose Duenas

Prodigy 60 points

Hello Jose,

I'm in need of RMS voltage of my input AC supply (230Vac, 50Hz). In my software, I can read my ADC for only 250ms once and adjust a gain parameter accordingly. I can do only very limited calculations on my ADC result.

To achieve this, I thought of using detecting peak voltage and calculating the RMS from that value.

Regarding the speed of my RMS measurement, response in a second is also OK.

Warm Regards,

Senthil

0 Senthil Prakash Jayaprakash over 12 years ago in reply to Senthil Prakash Jayaprakash

Prodigy 60 points

Hello Jose,

I'm attaching the circuit planned by me for this purpose.Confused due to different grounds used at high voltage side.

Please check and provide your feedback.

Regards,6507.pm_controller_ver2_0.pdf

Senthil

0 Harmeet Singh over 12 years ago in reply to Senthil Prakash Jayaprakash

TI__Intellectual 1550 points

Hi Senthil,

You can directly use the schematic as in the application note. Use pin 7 output and give it to your ADC input.

Measure the max value and the minimum value. The difference between the two will give you peak to peak voltage.

half of it will give you the peak voltage and divide/1.414 will give you rms. You just need to do scaling as well.

Hope this helps.

Regards,

Harmeet

0 Senthil Prakash Jayaprakash over 12 years ago in reply to Harmeet Singh

Prodigy 60 points

Hi Harmeet,

Thanks for your reply.

This is the solution we initial thought. But problem is, ADC should be read continuously to measure the max and min values. we can't offer microcontroller's processing power for this purpose.

Hence we look for a simple hardware solution which keeps the pin 7 output at peak value, so that we read the value directly on ADC at any time we need.

Regards,

Senthil

0 Harmeet Singh over 12 years ago in reply to Senthil Prakash Jayaprakash

TI__Intellectual 1550 points

Hi Senthil,

You can use Op amp as peak detector.

You will find circuit in any op amp book .

Regards,

Harmeet

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230Vac sensing using AMC1100