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Stimulus test gear

Discussion in 'Electronic Basics' started by Uriah, Sep 11, 2008.

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  1. Uriah

    Uriah Guest

    There is this digital scope sold by ABI that is called a circuit
    master. It does a number of things but one thing that seems unique is
    that it applies a DC current to a circuit while at the same time
    measuring the response. It is designed to apply this to a live
    digital circuit, with power on. This is mostly used on digital
    circuits. The idea is if you are measuring a circuit with 0VDC you
    can determine if it is short or open and a number of other things. It
    measures the response and shows it, along with the voltage measured.
    Is anyone familiar with this technique and can someone explain a way I
    can do the same thing using a regular scope? What do I need as a
    source? I think there is a little more to it then just using my bench
    power supply as the source. Is there any other gear that uses this
    technique?

    Thanks
    Russ
     
  2. Jasen Betts

    Jasen Betts Guest

    couple the calibration signal (or some other square wave) to the probe tip
    through an apropriately sized resistor.
     
  3. Ross Herbert

    Ross Herbert Guest

    :There is this digital scope sold by ABI that is called a circuit
    :master. It does a number of things but one thing that seems unique is
    :that it applies a DC current to a circuit while at the same time
    :measuring the response. It is designed to apply this to a live
    :digital circuit, with power on. This is mostly used on digital
    :circuits. The idea is if you are measuring a circuit with 0VDC you
    :can determine if it is short or open and a number of other things. It
    :measures the response and shows it, along with the voltage measured.
    :Is anyone familiar with this technique and can someone explain a way I
    :can do the same thing using a regular scope? What do I need as a
    :source? I think there is a little more to it then just using my bench
    :power supply as the source. Is there any other gear that uses this
    :technique?
    :
    :Thanks
    :Russ


    Seems to me to be a CRO with integrated digital voltmeter and function generator
    and some clever software to bring the functions together for ease of use.
    http://www.abielectronics.co.uk/Products/Circuitmaster4000.php

    By the look of it it isn't going to be cheap.
     
  4. Jamie

    Jamie Guest

    You must be very careful when doing that, many of today's circuits
    operate with components at a very low voltage level as their max
    voltage. Applying DC voltage to determine if a reference point is being
    pulled to common or just simply opened could cause damage.

    I guess you could work with a 1.5 volt DC reference via a resistor.
    I would suggest a R of 1 Meg. is using your scope. This should be
    sufficient to determine is a circuit is being pulled low or is simply
    opened.

    Even with DMM's in the diode mode, many of them apply 2 or more volts
    to the probes and normally use a 2k Scale as a 2.000 volt scale. This
    usually shows the Forward voltage of the diodes recognized in the field
    on low/medium voltage diodes.
    http://webpages.charter.net/jamie_5"
     
  5. It's not quite a TDR level of capability, but it's got AC signal
    injection, along with DC.
    It's basically designed for assembled board level testing, similar to
    the huge "flying probe" ATE testers that PCB assemblers have.
    It allows for signature analysis of assembled boards:
    http://en.wikipedia.org/wiki/Analog_signature_analysis
    You have to be careful with how you set up in-circuit testers like
    these, you can't just go probing things willy-nilly, the magic smoke
    will escape.

    It's a pretty specialised thing, I don't know what use it would be to
    you to have this capability in your own scope.

    Dave.
     
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