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  • Category Archives _diy Lab Instruments
  • OP Amp 0.1 -10Hz Noise Measurement.

    Here i will show my version of thei Linear Technologies 0.1-10Hz Test circuit which they publish in several Datasheets.
    It is a Gain of 5 non inverting amplifier. The OP Amp is  an LT1001.
    Here is the schematic.

    0.1-10Hz gain of 5 Schematic

    For low Noise and to avoid other mains interferences, it’s recomendet to Power the Amplifier wirh Batteries. Therefore I use two 9 Volt blocks.
    I build the circuit on flying on a single side copper board which i use as a ground plane.

    Here some pictures from the bench.
    in the box_web

     

    Some measurements:

    GND Noise_web
    Filter Circuit grounded.

     

    OP07 Noise_web
    OP07 noise 0.1-10Hz  100nV/DIV

     

     

    LF356 Noise_web
    LF356 0.1-10Hz 100nV/DIV

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  • DC Null Voltmeter

    For measuring low voltages especially the differences between two Voltage References I build the DC Null Voltmeter from Conrad Hofman.
    The Mini Metrology Lab, Part 2

    This is a switchable chopper based (LTC1050) DC Amplifier with a max. Gain of 10000!

    For testing i build a Voltage DIvider with an Vishay CNS471A6.
    It is amazing to measure 10µV with common Multimeter in the 100mV Range.

    Here Pictures from the Bench.

    Null Voltmeter_web

     

    NullVoltmeter_2_web

    No Housing yet.

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  • LT1027 based 5V Voltage Reference

    For comparing my Voltmeters and because of deep interest I build a LT1027 based 5V Reference Voltage Source.

    LT1027 Schematic
    Schematic

    I build it Bird Nest style ( hope this is the right expression) on a single side Copper Board.

    The low noise Voltage regulator (LT1763) is mounted on a daughter board.

    LT1763 Board_web
    Daughter board with Voltage Regulator.

     

    Ref in Geh_web
    First test if it fits in the housing.

     

    Final build but some decoupling capacitors and the input protection diodes still missing.

    Ref 1027 Final_web
    Final Build

    The finished Refernze in Housing.

    Referenz Zu_web
    Reference in Housing-

    First measurements with my 4,5 digit handheld multimeter shows 4.997V

    After 30 days of continous running the measurement with a new calibrated 6,5 digit voltmeter shows between 5,00096 and 5,00097V.

    The oszilloscope pictures shows the difference between batterie and power supply operation.
    No Filter!

    All measurements are done with a 1:1 probe with the following settings:
    1mV/Div und 2mS/DIV

     

    GND Taste
    GND Button pushed.

     

    LT1027 15V NT
    Reference operated with a linear LM7815 based power supply. Not floating!!

     

    LT 1027 2 x 9V Block
    Reference powered with  9V Block batteries.

    I have build a 15V power supply with an electronic ripple rejection(it is from an German Electronic Forum) followed by an LM7815.

    Now floating!!

    The result is a line similar to the picture with the batterie operation. No ripple. The line is twice as thick ( hope this is the right expression)

    Oscilloscope picture follows…

    Links:
    Rippel rejection   German article in ELKO Forum
    LT1027 Kondensator Noise Reduktion  German thread in Mikrocontroller Forum

    Thanks to all supporting thread members.

    UPDATE 09.02.2014

    I put the whole circuit into styrofoam insulated Box and put a PTC-heater foil under the Metal case.

    Pack

    The Pack.

     

    Heater

    This is the PTC-heater Foil,  12Volt 3Watts. The heater is only controled with it built in PTC. I used a 12 V Switching Power supply for the heater and a linera voltage source for my reference.

     

    Here some measurements at different temperatures:

    Voltage Temperaturet

    My thermometer is not calibrated it started at 9° Celsius which is equal to the ambient temperature of 15°Celsius. Hope to get a better one the next days…

    Will be continued…

     

     

     

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