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[jayb79]

I have got a VDO pressure sender (11-180ohm) working with bar on the SYL1813, but can not figure out how to get PSI to come out correctly.
I got this working with a transducer by multiplying the Pul and Puh by 14.5 but that does not seem to work here.
Can anyone help?

[jayb79]

I have some more info. I do not have a 10bar VDO but an 80psi or 5.5bar sender. At zero psi I am measuring 12ohms at 30psi it is about 77ohms and at 80 psi its 180ohms. I used and potentiometer to set the PuL to -1.6 and PuH to 148. I would love to know how to calculate it.

[colnny]

Do you have the data sheet for the sender? According to your measurement, the output of the sender is not linear.

[jayb79]

I do not have a data sheet. It is a low cost ebay sender. Here is the data I collected with an accurate large dial pressure gauge.
16ohm @6psi
25@10
57@20
77@30
108@40
125@50
148@60
165@70
180@80
it tops out at 186ohms @ 94psi.
The  SYL1813 seems to work well with the settings I have but it does read about 4.8 with zero pressure on it.
I have tried 2 other transducer type senders (one of them from this site and one from ebay) but they do not hold up well in the engine compartment or maybe its the diesel oil they don't like.

[jayb79]

more info, i plotted the ohms (left side) and psi (bottom) to get the formula, but i don't now how to apply it.


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[colnny]

I don't think the equation you got is right for the data.
I got a new one according to the data you provided.

pressure= 0.4378* resistance -3.164
When resistance is 0, pressure is -3.164, when resistance is 375, pressure is 161.011.

You just need to set the inty to 375r(0-375ohm), set the dot to 000.0, set the puL to - 3.16, PuH to 161.0.

[colnny]

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[jayb79]

Thanks, I feel like a dummy because I can't figure out how the math works to come up with the numbers.