MSP430F5529: ADC sample collection issue

PRASIDDHNATH YADAV

Prodigy 50 points

Part Number: MSP430F5529

Hi all,

I am using MSP430F5529 Launch Board, Trying to measure AC current across burden resistor,

ADC 12 bit resolution, ADC interrupt is generated for 1ms and sample collection is done accordingly,

I am collecting total of 20 sample.

The Problem i am facing is the positive ADC sample is getting properly store in the array,

but at the time of negative sample collection its showing 0 in the array.

Kindly help for the same.

over 3 years ago

0 Keith Barkley over 3 years ago

Guru 43535 points

By itself an MCU can't measure negative voltage, and in fact it may damage the ESD diodes.

0 Luke Ledbetter over 3 years ago

TI__Mastermind 27230 points

Hello,

The ADC on the MSP430F5529 is a single ended ADC. The input voltage range is from 0 - Vcc.

To read negative voltages, I recommend biasing your signal. The amount you bias will depend on your signal range but I recommend biasing to get the full scale range of the ADC.

Regards,

Luke

0 PRASIDDHNATH YADAV over 3 years ago in reply to Luke Ledbetter

Prodigy 50 points

Thanks for soon response,

can you help me to understand how can i bias my ac signal to get all sample in positive direction.

Regards,

0 Keith Barkley over 3 years ago in reply to PRASIDDHNATH YADAV

Guru 43535 points

If you use something like an AD8222 instrumentation amp, it has an offset pin built in. The Telemetry system I work with uses them for this exact purpose. Note you will have to have a negative voltage supply in the system.

One could say, why measure the negative peaks at all? I assume your signal is practically guaranteed to be symmetric.

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MSP430F5529: ADC sample collection issue