Digi-Panel Calibration?

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gmcnet1

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Apr 23, 2019
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I just replaced a broken engine temp sensor on my PO-installed Digi-Panel, and as with the old sensor (before it broke) the temp reads about 25
degrees low. My estimate is based on a reading from an IR thermometer pointed at the sensor which is attached to one of the thermostat bolts. My
analog gauge reading (non-stock) is comparable to the IR reading.

Can the Digi-Panel temp reading be calibrated, or is there some other common issue that might cause this symptom? Maybe a dirty connector at the back
of the Panel or something?
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA
 
Surface temp of the item and the actual temp at the sensor tip could vary a large amount as you are reading surface temp compared to the liquid temp.

JR Wright

>
> I just replaced a broken engine temp sensor on my PO-installed Digi-Panel, and as with the old sensor (before it broke) the temp reads about 25
> degrees low. My estimate is based on a reading from an IR thermometer pointed at the sensor which is attached to one of the thermostat bolts. My
> analog gauge reading (non-stock) is comparable to the IR reading.
>
> Can the Digi-Panel temp reading be calibrated, or is there some other common issue that might cause this symptom? Maybe a dirty connector at the back
> of the Panel or something?
> --
> Christo Darsch
> GMC Nor'easters
> 1977 Eleganza II - "The Komet"
> 3.50 Power Drive, Disc Brakes, Alcoas
> Weymouth, MA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
The IR reading is also subject to emmissivity errors. All surfaces emit different amounts of IR for the same temp
________________________________
From: Gmclist on behalf of John Wright via Gmclist
Sent: Tuesday, June 2, 2020 9:23 PM
To: gmclist
Cc: John Wright
Subject: Re: [GMCnet] Digi-Panel Calibration?

Surface temp of the item and the actual temp at the sensor tip could vary a large amount as you are reading surface temp compared to the liquid temp.

JR Wright

>
> I just replaced a broken engine temp sensor on my PO-installed Digi-Panel, and as with the old sensor (before it broke) the temp reads about 25
> degrees low. My estimate is based on a reading from an IR thermometer pointed at the sensor which is attached to one of the thermostat bolts. My
> analog gauge reading (non-stock) is comparable to the IR reading.
>
> Can the Digi-Panel temp reading be calibrated, or is there some other common issue that might cause this symptom? Maybe a dirty connector at the back
> of the Panel or something?
> --
> Christo Darsch
> GMC Nor'easters
> 1977 Eleganza II - "The Komet"
> 3.50 Power Drive, Disc Brakes, Alcoas
> Weymouth, MA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

_______________________________________________
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Unsubscribe or Change List Options:
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Automotive gages and warning lights, buzzers, etc. are notoriously
inaccurate. They approximate a S.W.A.G of actual readings. They are
extremely voltage sensitive, something that varies a goodly amount in a 40
year old vehicle. What they do a fair job of, is changes in what is
considered normal. As in no oil pressure where there used to be plenty, or
overheating.
Jim Hupy
Salem, Oregon

On Tue, Jun 2, 2020, 7:48 PM Keith V via Gmclist
wrote:

> The IR reading is also subject to emmissivity errors. All surfaces emit
> different amounts of IR for the same temp
> ________________________________
> From: Gmclist on behalf of John Wright
> via Gmclist
> Sent: Tuesday, June 2, 2020 9:23 PM
> To: gmclist
> Cc: John Wright
> Subject: Re: [GMCnet] Digi-Panel Calibration?
>
> Surface temp of the item and the actual temp at the sensor tip could vary
> a large amount as you are reading surface temp compared to the liquid temp.
>
> JR Wright
> > On Jun 2, 2020, at 7:28 PM, Christo Darsch via Gmclist <

> >
> > I just replaced a broken engine temp sensor on my PO-installed
> Digi-Panel, and as with the old sensor (before it broke) the temp reads
> about 25
> > degrees low. My estimate is based on a reading from an IR thermometer
> pointed at the sensor which is attached to one of the thermostat bolts. My
> > analog gauge reading (non-stock) is comparable to the IR reading.
> >
> > Can the Digi-Panel temp reading be calibrated, or is there some other
> common issue that might cause this symptom? Maybe a dirty connector at the
> back
> > of the Panel or something?
> > --
> > Christo Darsch
> > GMC Nor'easters
> > 1977 Eleganza II - "The Komet"
> > 3.50 Power Drive, Disc Brakes, Alcoas
> > Weymouth, MA
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
 
The Digi-Panel sensor is a surface sensor, not a liquid sensor.
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA
 
My Digi-panel reads pretty close... considering each LED on the engine temp scale is 15F.

I have fuel injection using the the EBL system. It has its own temperature sensor and I generally have the WUD (What's Up Display) running on my
laptop for fun. I have a 180F thermostat which the EBL reports runs 180-185F and the Digi-panel shows the 175 to next LED higher lit.

I'm an electronics guy so of course I looked at the Digi-panel circuitry, but that was 6 or 7 years ago. There are no connectors from the sensors,
they are wired right to the board (unless that has changed). I remember one large trim pot in there, but I can't say I remember any other pots. The
circuitry appears to be circa 80's -90's, through-hole technology. It just uses the common bar-dot LED driver chips.

Here is the spec sheet on the IC's. From this you should be able to reverse engineer the circuit and adjust the input voltage to the IC.

https://www.ti.com/lit/ds/symlink/lm3914.pdf

--
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
 
I'm not really an electronics guy, so if there isn't a trim pot for the temp sensors and there aren't any connectors that could increase resistance
(creating the low reading I'm seeing), I'm pretty much out of luck. Might just have to use it as suggested, as a guideline for what's normal. Thanks
though!
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA
 
I have a good VOM but I don't have the curves. I suppose I could call Applied and see if they have any of that info and are willing to share it --
they bought out the mfr a few years back.
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA
 
Thanks!
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA
 
I opened the case and found that there's a trim pot for all four gauges. Problem solved.
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA
 
As a rule the calibration remains without adjustment , but it could be the
thermocouple as we change part suppliers .
Call us if you need calibration so you can send it to our ave guys .

On Sun, Jun 7, 2020 at 10:35 AM Christo Darsch via Gmclist <

> I opened the case and found that there's a trim pot for all four gauges.
> Problem solved.
> --
> Christo Darsch
> GMC Nor'easters
> 1977 Eleganza II - "The Komet"
> 3.50 Power Drive, Disc Brakes, Alcoas
> Weymouth, MA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk
http://www.gmcrvparts.com
1-800-752-7502
 
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