Need Help using Eval inamp 62rz to amplify a Hall sensor output voltage.

Hello I am pretty inexperienced with circuits. I have the Eval Inamp 62 Rz and I am trying to amplify a voltage I'm getting from a hall sensor. I'm pretty certain I will use an AD622 with a gain of 100 but I'm not certain on what needs to installed on the Eval Inamp 62RZ board to get my project working. I'm not entirely understanding whether I need to use dual supply or power supply and how these will change what is installed on the board. Or how to get a reference voltage to be 1/2 power supply voltage. I also am not sure whether I need to implement anything with the guards, and if so which guards?

Basically the idea I have to do is use a current provider to send current through my hall sensor, which will generate a voltage in a magnetic field, then I will take the two leads for the hall sensor (V+ and V-) to the Eval input, then use the Eval to amplify the voltage and lead that from the output into a lockin amplifier. If this is vague and not really helpful into someone guiding me into how to get the Eval inamp 62Rz to work for this project please let me know and I can clarify any statements.

Thank you very much,

Alex K

  • 0
    •  Analog Employees 
    on Nov 3, 2015 4:56 PM

    Hi Alex,

    Thanks for using ADI products in your application.

    The EVAL-INAMP-62RZ has its own user guide, the UG-261. For a quick start guide in using the evaluation board, kindly read page 4 to 6 of the user guide.

    Initially, the board is configured in dual supply. If you want to convert this to single supply, place W14 in the position marked with a ground symbol. When using dual supply configuration, usually the the REF pin is connected to ground, to do this just simply install a jumper at W12. If you want to use a single supply, it is important that the REF pin must be connected to an external source of Vs/2 or it depends on how much you want to set an offset to the output of AD622, to implement this just simply install the W13 jumper of the evaluation board.

    To set the gain of the AD622 to 100, place a 511 ohms resistor across the RG pins of the in amp.

    Guard drivers are important if you are using a long cable at the input of the instrumentation amplifier, so if you aren't using any you can disregard this on your circuit. Usually, cables has both shield to reduce the interference and noise pick-up and a signal conductor. You can ground that shield. However, there are some space between the signal conductor and the shield which acts like  a capacitor to ground. For in amp, CMRR is affected by imbalance of the capacitance at the inputs. So the purpose of guard driver is to drive the shield at same potential of the input signal instead grounding the shield, so that there's a 0V at the effective cable-shield-capacitance. So, it's like removing the effect of that capacitor.

    Also, kindly check the input and output voltage range of the AD622. Make sure that the input signals applied at the inputs of the in amp and your expected output are within the specified range stated on its datasheet. We have a useful tool in evaluating our instrumentation amplifiers : the Instrumentation Amplifier Operating Range Tool, this will help you to determine if the in amp is operating within its specs.

    I hope this helps.