Custom Probes

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Custom Probes

Postby GBR » Wed Sep 14, 2016 1:21 pm

Can anyone tell me if the custom probe software follows a charateristic curve or a liner relationship?

Most AMM's for example have a charateristic curve as in the example below;

Voltage Air mass Kg/h

1.484 8
1.582 10
1.790 15
2.274 30
2.887 60
3.626 120
4.473 250
4.940 370

Can the software have a polynominal option if it is only linear atm?
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Re: Custom Probes

Postby STC » Thu Sep 15, 2016 7:50 pm

Hi,
Not something I use much but I had a quick look and came up with this using a look up table. I'm thinking this will be as good as the number of lines in the table?
Air Mass Custom Probe.psprobe
(1.67 KiB) Downloaded 36 times
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Re: Custom Probes

Postby KimAndersen » Fri Sep 16, 2016 6:03 pm

I use the Curve Expert software to generate a complete lookup table based on specification from a datasheet or from a table output spec. with a XY axis.

By using this software you are able to expand the output specification from 10 datapoints to for example 256 datapoints - that way you get a more accurate table.

Link to Curve Expert software https://www.curveexpert.net/ :wink:

Here is a example from the from the software.

HFM 5 Bosch Air Mass Meter - 0281002421.jpeg
HFM 5 Bosch Air Mass Meter - 0281002421


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Re: Custom Probes

Postby STC » Fri Sep 16, 2016 7:34 pm

Kim, GBR

I'm thinking with that software we can go from, for example 8 known values as above to many more with some accuracy ?
Will it just draw a graph or will it also create a table ?

Air mass figures confuse me, never can retain the information in my brain that I think I should have. I always go by Voltage on a scope and for digital ones I use a math channel and get an analogue image to look at them.

I cant see how the graph or table above is going to help me diagnose an MAF or Air Mass, for sure the ECU will convert the Voltage to G/s or KG/h for me with accuracy. Especially on a car that has Actual Values for both MAF & MAF Voltage and I can graph the data. That could be a good or bad MAF ? In fact I could place a variable potentiometer in place of the MAF and increment the voltage as I wish very slowly and make create that table, then in turn a Custom probe.

My point being that it is not often the ECU ability to convert the Voltage that is the fault, always the MAF that converts the Air Flow to the Wrong Voltage.

The ECU will see a voltage and convert it to an Air Mass value using its internal table ? From the graph I have a table ?

I'm thinking along the lines of testing a Map sensor on a car with a Pressure / Vacuum Gauge comparing the needle to the live data - independent Verification with a Known Good, or Fuel Pressure on a test gauge to Live data.

Perhaps the way forward is a Known Good Test Air Mass in series, in the airflow with no air leaks in between the two ?? and of course a look up table ??
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Re: Custom Probes

Postby KimAndersen » Sun Sep 18, 2016 9:10 am

STC

STC wrote:Will it just draw a graph or will it also create a table ?


Yes the software will generate a table based on the curve finder in the program which you have to import into the picoscope software - it's really a simple process.

I've made some table manually were the outcome were misleading or simply wrong, because there was to few data points in my curve - which send me in a wrong direction in terms of the correct diagnose.


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Re: Custom Probes

Postby STC » Sun Sep 18, 2016 9:55 pm

Thanks Kim
Great information as always.

Once again, unless the ECU table is corrupt how is this of any use in a diagnostic situation ??

Independent verification with a known good has always been "King" in my world ???
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Re: Custom Probes

Postby GBR » Tue Sep 20, 2016 4:26 pm

My point being that it is not often the ECU ability to convert the Voltage that is the fault, always the MAF that converts the Air Flow to the Wrong Voltage.


What if you were to calculate air flow and wanted to measure it using the scope.
As an example we tune many vehicles, and without specified air flow for the new tune we often measure boost and would like to use a custom probe to validate the AMM readings.

Its not only AMM that have non linear outputs either.
Its just an idea, I'm sure it would be easy to add alongside the linear feature.
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Re: Custom Probes

Postby KimAndersen » Tue Sep 20, 2016 7:27 pm

GBR

If you don't mind - I made a file from the data you have in your first post and here is the result. I have expanded the lookup table a bit and convert the kg/h value into gram per second.

Import the maf calibration curve file into picoscope under custom probe settings and you should see g/s as output values from your Mass Airflow sensor.

MAF SENSOR OUTPUT.jpg
MAF SENSOR OUTPUT CURVE


Mass Airflow Sensor.psprobe
(3.3 KiB) Downloaded 23 times


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Re: Custom Probes

Postby FioranoCars » Mon Oct 17, 2016 11:19 am

KimAndersen wrote:I use the Curve Expert software to generate a complete lookup table based on specification from a datasheet or from a table output spec. with a XY axis.

By using this software you are able to expand the output specification from 10 datapoints to for example 256 datapoints - that way you get a more accurate table.

Link to Curve Expert software https://www.curveexpert.net/ :wink:


Hi Kim
Which version of this do you use, or feel would be fine for most of our "automotive" needs (in case you use it for more scentific uses!) ?

Thanks
Richard
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Re: Custom Probes

Postby KimAndersen » Mon Oct 17, 2016 12:01 pm

Hi Richard

I use the Curveexpert Professional https://www.curveexpert.net/products/curveexpert-professional/software to automotive use.

I don't know the difference between the two software they are selling as I have never used the GraphExpert Professional software. The CurveExpert software is easy to use when first you have been around in different settings as it is with alot of software.

The only thing/problem that I have with this software were, when you must import the generated file into the pico software then you must learn some new things. :wink:

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