Re: In search of a SunPro (& Duty Cycle?)

[steveb@newkla.kla.com (Steven Buchholz)]

PDQSHIP asked:
> 
> Yo steve, sorry to ask, but the function of this meter are what? certainly
> interested...
> 
> Scott
> 
... not sure if you mean the function of the meter, or how it's used ...

What it does... (from an earlier message)

I have a SunPro Model CP7678 meter.  It comes in an yellow/orange case.  
It looks like a standard DVM, with an LCD display at the top, a large 
rotary function select switch in the middle and three sockets into which 
the test probes can be plugged.  The function selector has settings for: 
DC Voltage, DC Current (15A), Resistance, Diode Check, Lo Tach, Hi Tach 
(x10), Dwell and Duty Cycle.  The Tach and dwell settings have 4,5,6 and 
8 cylinder settings.  It is water resistant and will automatically shut 
itself off after not being used for a few minutes.  

The primary utility of the thing is that it actually has a 5 cylinder set-
ting for tach & dwell :)  Granted that not too many of us worry about dwell 
in the general sense, but the meter also has a "duty cycle" setting.  This 
is useful on the '83 TQC because there is a frequency valve in the FI that 
can be monitored to tell if the computer is getting proper inputs from the 
OXS, throttle switches, etc.  It is also useful for the CIS-E engines, but 
I haven't had a need for any of that to date.

I got another message asking about what the duty cycle is used for.  Duty 
cycle indicates the percentage of time that a given regularly cycling signal 
is active.  A signal that is cycling active for 1 second and then inactive 
for 3 seconds has a 25% duty cycle (active 1 second out of four total seconds 
in the cycle).  A signal that is active for 0.025 seconds and then inactive 
for 0.075 seconds also has a 25% duty cycle.  The diagnostics in the Audi 
ECUs have been known to use measurement of duty cycle, and other than inter-
preting the output of a dwell meter, the SunPRO CP7678 is the only device 
I've seen on the market that has this feature.  This can be used on the idle 
stabilizer valve, OXS frequency valve, EHA, speedo sending unit, etc.

Hope this helps!
Steve Buchholz
s_buchho@kla.com