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Analog Input Conditioning for a data logger !

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ranaya

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hi every1....

I'm gonna implement a data logger which has 8 Analog input channels. my supervisor told me, that voltage input should be able to use for any voltage level, (can read mV and V/ max 25V). So even temperature sensor signal output can be attached to it. User should be able to select the sensor type through the application software.

For mV values, input should be amplified & for max voltage (25V) i have to bring it to 5V (for ADC of MCU).

How can i measure both readings from same analog input ? Do i have to use variable gain controller ?
 

Hi Ranaya,

With this wide range of mV to industrial 25V the key question is with what accuracy the analog signals need to be recorded. A programmable amplifier with such a wide dynamic range is not an simple task. For 10-bit resolution you might look at the iC-JX for industrial interfacing with reading analog signals in that range. Here you can find some solutions: iC-Haus Homepage - Welcome.

Enjoy your design work!
 
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    ranaya

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HTA said:
Hi Ranaya,

With this wide range of mV to industrial 25V the key question is with what accuracy the analog signals need to be recorded. A programmable amplifier with such a wide dynamic range is not an simple task. For 10-bit resolution you might look at the iC-JX for industrial interfacing with reading analog signals in that range. Here you can find some solutions: iC-Haus Homepage - Welcome.

Enjoy your design work!
Click to expand...

@HTA, Thank you for ur quick reply ! actually i dnt have a gud knowledge about industrial application... this will be helpful !!!
 

What controller are you using for this purpose?

You can have this:
A non-inverting amplifier with a gain of +10 (or adjusted as required) has its input connected to the voltage source. The output has a zener diode to clamp the voltage.
A voltage-divider to step down the +25V down to the required range (eg. max +5V).

These are both connected to the controller/ADC. The controller decides when to read from which input.

This, I think, is a simple method. However, it will either require a lot of ADC channels, or another interfacing circuit which the controller controls to connect the output of one of these stages to the controller input.

Hope this helps.
Tahmid.
 

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