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CSLA1CD current sensor output A/D conversion problem

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Zedman

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csla1cd

Please help me,

Iam trying to detect if there is any AC current flow in a wire. Iam using Honeywell CSLA1CD current sensor. It needs 12V and GND and outputs Vcc/2 +/- 50mV per Amper (flows through the wire).

So if there are 2 amps than I (should) get 6V + 2x50mV -> 6.1V
I would like to measure this with a PIC16F690's ADC channel 0, with the following small divider to divide the voltage into the 0-5V range.

76_1234813860.gif


The problem is if I measure the voltage in every second that I get the correct value for the 3.05V and than it starts to decrement and then back and decrement again and so on.

Why is this?
What am I missing here?
 

csla1cd ac sensor

I suspect that your sensor outputs instantaneous current (as opposed to RMS) and the oscillation that you see in the digitized data is an aliasing artifact.

BTW, here's a good group dedicated to sensors: **broken link removed**
 

measure output of hall effect sensor with adc

What do you mean by "instantaneous current"? The output current from the sensor changes?
If I measure the voltage gets to the ADC with a multimeter than it seems constant while the ADC value alternates.

thanks,
Zedman
 

csla1cd current sensor price

Zedman said:
What do you mean by "instantaneous current"? The output current from the sensor changes?
Click to expand...
Yes, the output of the sensor could be a 60Hz sinusoid. What do you see if you measure the output of your sensor with a scope? What does your A/D data show if you run DC through the sensor?
 

    Z

    Zedman

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current sensor

I'll check it with the scope when I get home later today and will post the results.
 

So yes.

The datasheet doesn't very clear on this, it outputs ~50mV / Amper / turns.
BUT just a small bump on the beginning of the 50Hz period not DC!!!

The main reason I had chosen this sensor over the toroid/opamp/adc version is the ease of the measurement of the linear DC output and the less part count.
It was 10 times more expensive than doing it with toroid.

And now I'll do it with a toroid, and have 2 of this sensors for sale.

thanks,
Zedman
 

I was just about to use this sensor myself on a data logger for power usage. After reading your findings, is it possible just to rectify and filter the output of the hall effect sensor and then feed that into the ADC of a PIC?

Cheers

Bj
 

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