# Stimulus test gear

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

1. ### UriahGuest

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 BettsGuest

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

3. ### Ross HerbertGuest

: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
ower 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. ### JamieGuest

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. ### David L. JonesGuest

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.