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XY Recorder Block Diagram & Working

  • An XY recorder plots the instantaneous relation between two variables. The writing pen will be deflected in both X direction and Y direction on a stationary chart paper. Depending on the desired application one or more write pens are used.

    XY recorders are also employed using proper transducers for recording of physical quantities as function of other physical quantities. The motion of the pen in X and Y directions is obtained by servomotors. A sliding pen and moving arm arrangement is used with X-Y recorders.



    (a) Description of the Block Diagram of an X-Y Recorder: 

    The block diagram is shown in Figure. From the block diagram we find that the X input and Y input are supplied to the error detector in series with the standard reference voltage offered by the internal reference source.
    The output of the error detector is given to a chopper. The servo amplifier is driven by the chopper. The amplifiers output drives the pen. The Y amplifier's output drives the arm. Square shaped graph paper will be used. It is fixed over a pad by electrostatic attraction or by vacuum.

    (b) Working: 

    The input signals are attenuated to around 0.5 mV which is withir the dynamic range of the recorder. Both X and Y signals are compared with the internal reference source. This is done in the balancing or Error detector block. The X and Y channel error output will be the DC error, which is the difference between the input signals and the reference voltage.
    The DC error signal of both channels is used in the choppers to convert it in to an AC signal. The magnitude of the AC output of the choppers is insufficient to drive the motors of the pen and the arm. Therefore the output of the two choppers will be amplified in the servo amplifiers. The servomotors drive the pen and the arm. The pen and the arm execute motion in proper direction to reduce the error. The movement of the pen and arm is to bring the system to balance. The variation of X and Y signals, move the pen and the arm in the appropriate directions to keep the system in balance. This movement produces a record of the signal components on the paper. It is to be remembered that the both X and Y channels and the total system works simultaneously.

    (c) Range:

     Input range variable from 0.25 V/cm to 10 V/cm
    Accuracy ± 0.3 % to ± 0.1 % at full scale.
    Slew rate and acceleration are important. Slew rate is expressed as displacement in second. Accelerating is expressed in cm/s. Slew rate refers to the movement of the pen in Y direction. Acceleration refers to the movement along X direction. Typical values of slew rate and acceleration are 97 cm/s and 7620 cm/s respectively with respect to high speed recorders.
    Sensitivity obtainable is around 10 micro volt/mm.
    Frequency response is around 6 Hz in both directions.

    (d) Variations in Design: 

    The X-Y recorder described above is of analog type. Digital X-Y plotters are available. These digital X-Y recorders employ stepper motors of the open loop type, instead of the servomotors used in analog recorders. Digital X-Y plotters have many advantages.

    (e) Advantages of Digital Recorders: 

    The following are the advantages of digital recorders
    1. Number of input channels can be provided for sampling and storage simultaneously.
    2. Number of desired trigger modes can be incorporated.
    3. They have the provision to display pre-trigger data.
    4. Multi-pen Multi Ink plotting is possible.
    5. Analysis of records with respect to data, time and setup condition is possible.
    6. They will be able to draw grids and axis.
    7. Communication interface facility with other digital equipment is possible.
    8. Desired specifications and functions are obtainable by the use of specially programmed software packages.

    (f) Applications: 

    X-Y recorders are used in recording:
    1. The speed torque characteristics of motors.
    2. Regulation characteristics of power supply
    3. Characteristics of electronic devices like transistors and diodes etc.
    4. Hysteresis curves, stress-strain characteristics.
    5. Electrical characteristics of material. Ex: Resistance versus temperature.


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