need help in electrical measurements(ISV)

[Konstantin Bogach]

Ero, thank you for this response.  It is strange that Audi manuls and SJM
(www.sjmautotechnik.com,  very good source) never mentioned 2 types ISV's and 2
method's of checking IS system.  I assume you are familiar with Audi if you read my
message. Bentley manual says only about mA measurement.
DMM was connected in series for current measurement.  I meant "infinity" ralative the
range.  You are right - "overflow" is the right term.

Thanks again.

Konstantin Bogach.

> From: Ero Rademer <erademer at igd.fhg.de>
> Hi!
>
> Konstantin Bogach wrote:
> > What I can not understand is why ISV buzzes
> > only if I use mA range on DMM?  If I use A or microA
> > it does not buzz and DMM shows nothing (.002 as with
> > open circuit).
>
> First of all, there are two types of ISVs, the one driven by
> a pulsating *voltage* (12V or 0V) and the length of the pulses
> defining how far the ISV opens. And the other one, which are
> powered by a varying *current* (around 400mA avg?) to control
> the valve.
>
> Second. If you use the wrong range on your DMM, the resistance
> of the DMM is bigger (microA) or lower (A). The ISV controller
> module senses this as an open circuit or a short in the lines
> to the valve and ceases operation until you restart the engine.
> Thus you do read no current (.002) in either range.
>
> > When I use mA range ISV buzzes and DMM shows 0L. which I
> > interpret as infinity.
>
> Rather means "overflow".
>
> "0L" is unusual for a simple off-the-shelf DMM. Normally, when
> operated in the wrong range, you will measure 0 (A, mA, uA,
> whatever you selected) if the current is too low to display or
> an "1.   " if the current is to big to display (over 2.00)
> Most cheap DMMs have an 200mA range and measuring 400mA result
> in an overflow. If you are measuring the first type of valves,
> the current is much higher (for short periods of time) than you
> can measure in the 200 mA range. Better measure the *voltage*
> across the ISV terminals range on them, the DMM will interpolate
> roughly and show between 2 and 7 volts when the ISV is working.
>
> There is no "infinity" when measuring voltages or currents.
>
> If you are a layman when it comes to electrics: Did you have
> hooked up your DMM correctly for measuring *current* (in series
> with the ISV) and not in parallel to it (for *voltages*)...?
>
> HTH
> So long!
> Ero.
>