Does your pyro zero out overnight?

[Radshooter]

Just wondering if my pyro is going psycho on me. When I start it up in the mornings, it will still be reading around 150* before I start the engine. The truck sits for 12-13 hours, and the temps have been getting down into the 50s overnight here. Sometimes if I tap the guage, it will drop to around 100*, but never goes to zero. It still seems to be working OK otherwise... fast response, and the driving temps appear to be in the usual range. Is this anything to be worried about? Does anyone else see this on their pyro? It is a pre-turbo Di-Pricol, installed by a dealer.



Thanks. .

Steve

 

[jcarey]

Mine does the same thing. I have a Dipricol pyro. I'd also like to know if that's normal.



Jim

 

[lschultz]

Add another one to the list mine does the same thing. Person I talked to at Genos said this is normal.

 

[XJSuperman]

Mine drops to about the 6 o'clock position when I shut the truck down. Then when I turn the ignition on (when first starting the truck) it points to about 100*... seems normal.

 

[Radshooter]

Thanks guys. I feel better knowing I am not unique!! But now I am wondering about something else... ... XJSuperman says his starts reading 100 when he turns on the ignition. To me, this implies that his is somehow needing electricity to give a temp reading, electricity that is not present unless the ignition is on. Everyone else's reads all the time. Are we hooked to electricity full time? Does the pyro need an outside electric source to read temps? I thought the di-electric probe provided the current to produce a temp reading. I thought I was getting this stuff all figured out, but apparently I've got a lot to learn. Thanks for enlightening those of us stuck in the fog.



Steve

 

[RustyJC]

Some pyrometers such as my Westach read directly from the millivolt output of the Type K thermocouple, so they read all the time - no outside power needed.



Other pyrometers use amplifier or control boxes between the thermocouple and gauge. If these amplifier/control boxes require outside power, chances are the gauge won't function when the amplifier/control box isn't powered up.



Rusty

 

[Radshooter]

Thanks RustyJC... . now that you mention the Type K Thermocouple, some of my memory is coming back. I remember the article about all the different guages in the TDR mag a while back.



Thanks... .

Steve

 

[rbattelle]

Mine (an Isspro) reads ambient temperature when I get up in the morning.

 

[fbaurley]

Type K thermocouples creat a voltage ( millivolts) when an increase in temperature occurs. The thermocouple creates a voltage, because the tip has 2 dissimiliar metals soldered together. This by some magic means creates a voltage when the temperature changes. This voltage correspondes to a certain temperature. There are also a few other types of thermocouples( Type J),but the operating principle is the same. Most pyrometers are RTD's, or resistance temperature devices. With an RTD a voltage is supplied, usually when the key is on, and as the temperature increases the resistance of the probe increasees, and therfore gives a voltage drop. The drop is is sensed and correlated to a certain temp.

 

[rbattelle]

Most pyrometers are RTD's, or resistance temperature devices.

While the remainder of your post is absolutely correct, I believe this particular statement is false. Most pyrometers are K-type thermocouples, not RTD's. Most temperature devices installed in liquids are RTDs (water temp, oil temp, transmission temp).

 

[bpenrod]

My Autometer guage sits at 6 o'clock until the key is turned on then it reads the ambient temp. Once the motor fires it climbs up but the colder the morning the lower the reading when the key is turned on.

 

[fbaurley]

I d have to check , but if i rememeber correctly most rtds have 3 wires going to the unit, where as a thermocouple will have 2. For a thermocouple to be accurate it must be hooked into a cold junction board. a cold junction board uses a thermistor to give a baseline temperature. This is needed , because a thermocouple, only measures the change in temperature. From my experiance Rtd's are more durable, than thermocouples. Therfore on most vehicle applications they are used. Vibrations are hard on thermocouples. If you are paying $150 to 175 for a thermocouple, you are getting screwed, good lab grade thermocouples can be purchased for arond 60 to 80 bucks, but the cheapest rtds are over $100 Most of the pyrometers that i have been around are newer oem applications, that use an RTD.

 

[RustyJC]

My Westach uses a Type K thermocouple. In the industrial engines and gas turbines built by our company, we use both thermocouples and RTDs, but thermocouples are used for exhaust temperature measurements.



Rusty

 

[JeffJackson]

The problem with thermocouples is that they approach linear output only over a certain range of temperatures. I don't have my data here at home, but I'm guessing the type K thermocouple is linear over a range of about 500-1500 degrees. That's why you don't see the gauge read room temperature correctly.

 

[rbattelle]

From my experiance Rtd's are more durable, than thermocouples. Therfore on most vehicle applications they are used. Vibrations are hard on thermocouples. If you are paying $150 to 175 for a thermocouple, you are getting screwed, good lab grade thermocouples can be purchased for arond 60 to 80 bucks, but the cheapest rtds are over $100 Most of the pyrometers that i have been around are newer oem applications, that use an RTD.

Can you cite a new OEM engine that came equipped with a RTD pyrometer? It would seem to me that the very high thermal inertia of an RTD would preclude their use on engines with wide operating ranges. With all due respect, I'm skeptical.



Although it's true that lab-grade thermocouple wires are quite inexpensive, I'd stop short of saying anyone is "getting screwed" by paying $150-$175 for a pyrometer which includes a gauge, lead wires, calibration, and a stainless-steel ruggedized thermocouple enclosure.