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#1
08-09-2006, 07:43 PM
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Quote:
I am under the impression that the early M103 engine X11 port is properly read (by a sears type multi meter with duty cycle setting) with the (+) lead in pin #2 and the (-) lead in pin #3... this is due to the % ON bias of the multi meter in question?
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-Marty 1986 300E 220,000 miles+ transmission impossible (Now waiting under a bridge in order to become one) Reading your M103 duty cycle: http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13 http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14 
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#2
08-10-2006, 03:31 PM
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The manual for that meter states the duty cycle measure is for ON pulse width, from 100us-100ms [ which is 0.1%-99.9 %] My info shows Benz uses Off cycle for duty percentage. [ meaning a correct reading with that meter requires reverse polarity of leads]
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#3
08-10-2006, 04:15 PM
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Thanks Arthur that helps a lot... Mercedes always does it one way but meters vary...
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-Marty 1986 300E 220,000 miles+ transmission impossible (Now waiting under a bridge in order to become one) Reading your M103 duty cycle: http://www.peachparts.com/shopforum/showpost.php?p=831799&postcount=13 http://www.peachparts.com/shopforum/showpost.php?p=831807&postcount=14
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#4
08-11-2006, 11:30 AM
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Mark....
Clearly for me the mistake you are making is in your first post.... Step 3.........   Quote:
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2009 Mercedes ML320 Bluetec
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#5
08-11-2006, 11:41 AM
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I could not find anywhere in the manual where it states that the meter uses the ON pulse width. I called EXTECH (mfg for this Sears multimeter) and tech support confirmed that they have no documentation stating such. I relayed my story of checking the meter against the Indy MB mechanic's duty meter and he concluded that the meter appears to be displaying ON vs OFF as a %. Based on this info, I would suspect that we have a few members of this forum that are running lean at 65% instead of the 45% they think they have their car set at. Interesting...
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#6
08-11-2006, 11:52 AM
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<
Well , how I read that is PULSE WIDTH is ON , because NO pulse width would be OFF.[ meaning NO signal] The point I was making is BENZ specs for DUTY CYCLE is the opposite of American duty cycle, where Benz % specs are OFF %, rather than ON %. I will do some homework and find that info..I had a site that explained better than I ... I just have to re-find it.. .anyone else have that info???? Last edited by Arthur Dalton; 08-11-2006 at 12:06 PM.
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#7
08-11-2006, 11:54 AM
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My bad typo. Sentence should read: .... I would suspect that we have a few members of this forum that are running lean at 55% instead of the 45% they think they have their car set at.
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#8
08-11-2006, 12:55 PM
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You can verify by just using normal voltage and the formula!
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~Jamie _________________ 2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's. 1986 190E 2.3 Black, Auto, Mods to come soon.....
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#9
08-11-2006, 02:01 PM
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It seems to me a simple test would be connect to +12 and it will read 100% and then connect to ground and it will read 0%. I was a bench tech and the MB system of measuring the "percentage off" duty cycle does not strike me as odd since "low side switching" is very common in control systems. You could reverse your leads as stated or just subtract the number from 100. Mike
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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine) 1988 F150 144,000 miles (leaks all the colors of the rainbow) Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
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#10
08-11-2006, 06:45 PM
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Quote:
I ran the test you suggested with one modification. If you connect the red probe to +12v and the black to ground you do not get any reading since the meter is looking for a pulse signal. So I lifted one of the probes for a split sec a few times and the meter read in the high 90% range. When I reversed the leads and did the test again, it read in the low single digits %. I would say that this confirms that this hand held meter reads % ON. The EXTECH support dude said that all of their meters function in this same manner. He thought you would need to get a higher end scope for it to display the % OFF that Mercedes uses (or as I suggested to him, just reverse the leads on the cheap meter).
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#11
08-11-2006, 06:56 PM
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The test has to have a pulse to read a duty cycle. .and the pulse has to be within the specs of the meters capacity to read it.
Straight 12v will not have a duty cycle and 100% can not be read by the meter, as 100% is NO duty cycle. So, your test of interrupting the signal does verify an ON duty cycle meter.
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#12
08-11-2006, 07:04 PM
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You are correct. Some Extech specs I have here on one of their meters says the PWM range is .4% to 99.6%. So at 0 or 100 you will just get "OL" or whatever as you said. I agree the test you did is a good test and confirms what you thought. Pretty clever reveresing the leads. I don't think I would have thought of that!
Mike
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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine) 1988 F150 144,000 miles (leaks all the colors of the rainbow) Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
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