It doesn't make any difference what you use to calibrate or check
calibration of a pressure device. PSIG is PSIG. or what ever scale you
decide to use. Granted there is a very small amount of compression as
the pressure increases but that equalizes very quickly. I have been in
the instrument design business for 30 years and I would suspect that the
nonlinear is the construction of the internals of the unit. I have
found that unless you are using a first quality units no 2 OEM type
automotive pressure sender are the same. I would suspect that if you
got another sender that you would find a completely different
calibration curve. They are design to function within a pressure band.
My choice would be to return the sender and get another one and check it
and see if it is the same.
J.R. Wright
GMC GreatLaker
77 Eleganza II
Michigan
>
> -- [ From: Eugene Fisher *
EMC.Ver #2.5.3 ] --
>
> I wonder if part of this non-linear operation might be because you used
> air which can compress with some mechanical resistance. I wonder if you
> used water or oil if it would have been different since they do not
> compress.
>
> gene
> -------- REPLY, Original message follows --------
>
> Date: Tuesday, 25-May-99 02:51 PM
>
> From: Dave \ Internet: (dgmdgm)
> To: gmclist \ Internet: (gmcmotorhome
> .org)
>
> Attachment:
mimemsg.doc Code: 026FS9J \ Created: Unknown [3 Kb]
>
> Subject: Re: GMC: Oil Pressure Sending Unit
>
> >Turned up this in a archive search:
> >
> >Wells PS-136 (?)
> >NAPA (60) OP6636 (about $17)
> >NAPA (80) OP6638 ( same )
> >GM Delco (new number)15591103 (about $43)
>
> I recently replaced mine with a Standard PS-154. I checked the
> calibration (using air pressure) before I installed it and was kind of
> surprised at what I found.
>
> It seems that the sending unit is very non-linear and has very crude
> resolution. The gauge moves in distinct steps as the pressure rises and
> falls, especially at the low end of its range. For example the first
> step was from 0 to 1/8 scale at 13 psi. There where a couple more steps
> from 1/8 scale to 1/4 scale at 15 psi. After that the steps where
> smaller. Here are the measurements (gauge vs. pressure):
>
> Gauge Pressure
> ----- ---------
> 1/8 13
> 1/4 15
> 1/2 25
> 3/4 40
> Full 60
>
> If anyone else has done this test with their sender I would be
> interested in comparing the results. My feeling is that this is a very
> low quality sender.
>
> Dave
> 73 Sequoia
>
> -------- REPLY, End of original message --------
>
> --
> Gene 76Palm Beach /Or/CA
>
> GMC Technical Information
>
http://www.california.com/~eagle/
wner-gmcmotorhome]On Behalf Of Billy Massey
