[Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?

[Mike]

At 12:40 AM 24/05/05, you wrote:
>there are a lot of ways to do it.  That's how I managed it.

Nothing personal, I was chuckling (as it were) at that very
point, there are a huge number of ways one could implement
an instrument with hysteresis. Most common way is certainly
variations on opamps, differential or single ended. I've seen
some doozies in my time, the thing I find curious is the
efforts to go and handle a hysteresis by a contrived device
like an opamp - a device created to circumvent many non linearities
when the simplest unitary devices suffice quite well in as much
as the non-linearities can be selected so easily to match the
task without needed any opamps.

I just find it ironic the very devices crafted to be as linear as possible
use inherent nonlinear devices more suited directly but,  still economical
that a complex device like an opamp is so cheap and readily
available when simpler devices might be considered elegant by many
engineers but the sad thing is the time spent explaining how to use
them is worth more than the opamps, or even the articulation herein.

;-)

Mike





>Dan Nicoson
>
>
>> -----Original Message-----
>> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
>> Behalf Of Mike
>> Sent: Monday, May 23, 2005 12:14 PM
>> To: diy_efi at diy-efi.org
>> Subject: RE: [Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?
>>
>>
>> mmmmm, hard way to do it - imho
>>
>> I think there is an easier way
>>
>> <chuckle>
>>
>> Mike
>>
>>
>>
>> At 11:42 PM 23/05/05, you wrote:
>> >To measure the pulse width of both a hi impedance and lo impedance (P&H)
>> >injector I would take the signal between the injector and the computer's
>> >transistor.  Use a comparator to create a nice clean square wave
>> to measure.
>> >
>> >For a hi impedance injector you will see the voltage go from 12-14 volts
>> >down to 0 - .6 volts as the injector opens.  The voltage will stay there
>> >until the PW is over going back up.
>> >
>> >For the low impedance, you will see the voltage drop as
>> described above and
>> >then go back up to 8 volts or so for the hold portion.
>> >
>> >I would use a comparator to create your square wave.  Set the
>> reference so
>> >the comparator trips around 10 volts, this will ensure you can
>> then measure
>> >both hi & low impedance injector pulswidths.
>> >
>> >Go to Digi-Key.com and download the data sheet for a LM398.  This is a
>> >sample & hold chip.  I used two in series to create a very nice steady
>> >output on my project.  The data sheet will have example circuits
>> to help you
>> >figure the rest of the circuit out.  You will also need negative voltage
>> >supply for use with this chip, I used the ICL7660.
>> >
>> >The 8 & 10 volts mentioned above are approximate.  You may find starting
>> >voltages approaching these values (hope not) and that may or may not be a
>> >problem for you.
>> >
>> >Also, be aware of the inductive spike as the injectors close or the P & H
>> >goes from Peak to hold.  Your circuit may need some diode therapy to deal
>> >with these.  I used a combination of high resistance on the
>> input from the
>> >injector line and some diodes to keep the spike out of my circuit.
>> >
>> >I have a write up on my sequential secondary injection system on
>> my web site
>> >www.myo-p.com  I used three channels of feed back on that circuit.
>> >
>> >Have fun.
>> >
>> >Dan Nicoson
>> >
>> >
>> >> -----Original Message-----
>> >> From: diy_efi-bounces at diy-efi.org
>> [mailto:diy_efi-bounces at diy-efi.org]On
>> >> Behalf Of gary
>> >> Sent: Sunday, May 22, 2005 2:47 PM
>> >> To: diy_efi at diy-efi.org
>> >> Subject: Re: [Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?
>> >>
>> >>
>> >> (P)eak & (H)old.....  low impedance injector
>> >> In reference to post below, the electronic kits and/or assembly
>> >> books for such kits, for injector DC monitoring and to allow
>> >> monitoring of P & H injectors can be can be obtained through
>> >> AutoSpeed and Silicon Chip, both native of your country.
>> >>
>> >> GAS
>> >>
>> >> ----- Original Message -----
>> >> From: "Mike" <niche at iinet.net.au>
>> >> To: <diy_efi at diy-efi.org>
>> >> Sent: Sunday, May 22, 2005 1:29 PM
>> >> Subject: RE: [Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?
>> >>
>> >>
>> >> > At 08:32 PM 22/05/05, you wrote:
>> >> > I have seen a kit that converts a P&H waveform into an equivalent
>> >> > simple pulse waveform, expressly for the purpose of duty cycle
>> >> > measurement.  It uses a dual op-amp IC and a handful of other small
>> >> > components.  I have a magazine article that
>> >> >
>> >> > Sorry I'm missing something here - whats P & H ?
>> >> > Did u mean Pulse Width ?
>> >> >
>> >> > Regards from
>> >> > Mike Massen
>> >> > Perth, Western Australia
>> >> > VL Commodore Fuse Rail that wont warp or melt !
>> >> > Twin Tyre rims and tyres for sedans
>> >> > http://niche.iinet.net.au
>> >> >
>> >> > > describes it.  Let me know if you need more info, or contact me
>> >> > > off-list if you'd like the name of the kit retailer.
>> >> > >
>> >> > >Cheers
>> >>
>> >> _______________________________________________
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>> Regards from
>>
>>
>> Mike Massen
>> Perth, Western Australia
>> VL Commodore Fuse Rail that wont warp or melt !
>> http://niche.iinet.net.au
>>
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