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Beginner AD623 Questions

Question asked by madvoid on Jan 6, 2012
Latest reply on Mar 17, 2013 by rafp

Hi all,

 

These may be very basic but I had a few questions about the AD623 and its application.

 

1. I am trying to amplify the signal from a Licor li200 pyranometer to be read by a microcontroller (See attached picture for diagram).  The pyranometer has a current output so I bridged the leads with a 147-ohm resistor and I am using the voltage drop across the resistor as the input to the AD623.  The maximum expected voltage from the sensor is approximately 15 millivolts so the potentiometer is set to produce a gain of ~325.  Is this setup acceptable for what I am doing? I am trying to minimize error.  In the schematic, the op-amp is powered from a regulated 5V supply and the output of the op amp leads to my ADC for the microcontroller.

 

Li200 W: AD623.jpg

 

2. I am trying to amplify a maximum sensor output of 15 millivolts to as close to the rails as possible.  According to the datasheet, 0.5 Volts below the voltage source is the closest I can come to the rails.  Is it acceptable design to set the gain so the limits are reached?

 

3. What is the best way to quantify error introduced within the AD623? So far I have been using the basic gain error but is there anything else that should be factored in?

 

Thank you in advance for any help, it is greatly appreciated!  I'm sorry if these questions are very basic.

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