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#1
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Electrical loading of MAF sensor output...
Hello there,
I am designing an auto accessory that would respond to the MAF sensor voltage (0-5v analog GM/Bosch style). I will therefore need to tap into the MAF sensor signal which is being sent to the ECM. My question is relating to the input impedance of my accessory. What shall the minimum input impedance be such that the original MAF sensor signal feeding the ECM is unaffected? I cannot find any specifications that deal with this topic. For instance would an input impedance of 90kohms be acceptable? Any help or references would be very nice indeed, thx, frenchy |
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#2
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Electrical loading of MAF sensor output...
The obvious answer is the more impedance the better. Ask Heisenberg. I would
imagine that there is not much current in the circuit. Modern Multimeters are 10 megaohms to minimize the effect on a circuit. You load seems a little low but the only way to know is to test it yourself. Apply a load and measure the voltage drop. When it is low enough it is good. I would say not more than .05V. "frenchy" > wrote in message oups.com... > Hello there, > > I am designing an auto accessory that would respond to the MAF sensor > voltage (0-5v analog GM/Bosch style). I will therefore need to tap > into the MAF sensor signal which is being sent to the ECM. My > question is relating to the input impedance of my accessory. What > shall the minimum input impedance be such that the original MAF sensor > signal feeding the ECM is unaffected? I cannot find any specifications > that deal with this topic. > > For instance would an input impedance of 90kohms be acceptable? > > Any help or references would be very nice indeed, > thx, > frenchy > |
#3
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Electrical loading of MAF sensor output...
Scott Buchanan wrote: > The obvious answer is the more impedance the better. Ask Heisenberg. I would > imagine that there is not much current in the circuit. Modern Multimeters > are 10 megaohms to minimize the effect on a circuit. You load seems a little > low but the only way to know is to test it yourself. Apply a load and > measure the voltage drop. When it is low enough it is good. I would say not > more than .05V. Scott, Thank you for your reply. I do not have any MAF sensors here in my design lab, which is why I am researching this. I want to simulate it here in my lab 1st, then indeed I will test my prototype on real vehicles. Certainly there must be some printed specs regarding MAF sensor output impedances or a discussion on loading. thx, frenchy |
#4
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Electrical loading of MAF sensor output...
frenchy wrote:
> > Hello there, > > I am designing an auto accessory that would respond to the MAF sensor > voltage (0-5v analog GM/Bosch style). I will therefore need to tap > into the MAF sensor signal which is being sent to the ECM. My > question is relating to the input impedance of my accessory. What > shall the minimum input impedance be such that the original MAF sensor > signal feeding the ECM is unaffected? I cannot find any specifications > that deal with this topic. > > For instance would an input impedance of 90kohms be acceptable? > > Any help or references would be very nice indeed, > thx, > frenchy The ecu is ttl and cmos. I would try to get at least 10 meg ohms. IMO, 90k would NOT be acceptable. Nor would 900k. |
#5
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Electrical loading of MAF sensor output...
frenchy wrote:
> > Hello there, > > I am designing an auto accessory that would respond to the MAF sensor > voltage (0-5v analog GM/Bosch style). I will therefore need to tap > into the MAF sensor signal which is being sent to the ECM. My > question is relating to the input impedance of my accessory. What > shall the minimum input impedance be such that the original MAF sensor > signal feeding the ECM is unaffected? I cannot find any specifications > that deal with this topic. The higher, the better. 100K would be good, 1 megohm would be better. Be careful not only of loading the sensor with a low impedance but of conducting external interference back into the ECM through your device. A better (but more complex) solution would be to read the OBD II data and get the air flow value from that, scaled to pounds per second or whatever. -- Paul Hovnanian ------------------------------------------------------------------ Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam. (Translation from Latin: "I have a catapult. Give me all the money, or I will fling an enormous rock at your head.") |
#6
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Electrical loading of MAF sensor output...
I would be surprised if there was anything in the public domain. It is too
esoteric. The only place you may find any documentation is in the engineering departments of auto manufactures. Not to tell you what to do, but if you are going to properly develop your product, you will need a test bed in your lab. Obtaining parts from a yard would be a good bet. In the mean time, I would tap into the circuit of a car to do the testing and get the information that you need. If you can share, I am curious what you are doing. If you need a tester let me know. "frenchy" > wrote in message oups.com... > > Scott Buchanan wrote: > > The obvious answer is the more impedance the better. Ask Heisenberg. I would > > imagine that there is not much current in the circuit. Modern Multimeters > > are 10 megaohms to minimize the effect on a circuit. You load seems a little > > low but the only way to know is to test it yourself. Apply a load and > > measure the voltage drop. When it is low enough it is good. I would say not > > more than .05V. > > > Scott, > Thank you for your reply. I do not have any MAF sensors here in my > design lab, which is why I am researching this. I want to simulate it > here in my lab 1st, then indeed I will test my prototype on real > vehicles. Certainly there must be some printed specs regarding MAF > sensor output impedances or a discussion on loading. > > thx, > frenchy > |
#7
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Electrical loading of MAF sensor output...
frenchy wrote: > I am designing an auto accessory that would respond to the MAF sensor > voltage (0-5v analog GM/Bosch style). I will therefore need to tap > into the MAF sensor signal which is being sent to the ECM. > For instance would an input impedance of 90kohms be acceptable? I thought that platinum MAFs had only a few hundred ohms resistance, but according to this thread it's higher: http://www.innovatemotorsports.com/f...hp/t-1399.html Is there any reason why your accessory's input impedance will be 90K? Why can't you use a buffer IC and get much higher impedance/ |
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