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

[Andrew Hopton]

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 
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

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org] On
Behalf Of Marcello A. Belloli
Sent: Sunday, 22 May 2005 1:01 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] Measuring Pulse Width/Duty Cycle of an Injector?

Hello Everyone,
     I'm still working on a datalogger project.  Been doing a lot of the
software while I've been on vacation in Thailand. I'm still on
vacation, but can't keep my mind off of this project.  I'm using a
PIC18F452 as the Micro behind my datalogger.  I've got just about
everything working.  The one place I'm having problem is the
understanding of how to read pulse width of a fuel injector.
     Is there a way of looking at all types of injectors, that will allow
for an accurate account of timing?  I've been looking at two type of
injector firing.  Low resistance injectors, which use a driver that
duty cycles the injectors after the main firing to keep the current
within limits.  And Higher resistance ones where the resistance alone
keeps the current down.  Now how do you look at firing time of an
injector when the driver starts to duty cycle it after 1.2ms?
     I guess I have one more question too - What is the best way to
connect to a circuit like an injector driver output?  I figure I only
really need timing information.  I want to keep the voltage between
0-5 volts and apply as little load to the circuit as possible.
     After looking at this I can understand why my multimeter that has a
PulseWidth setting has trouble sometimes.
     Any ideas would be great.    Thanks,  Marcello
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