Wrong readings CHT and EGT or defect dynon?

[PieterNL]

For a normal situation to the following strange measurements…

CHT
- Gives random values on the Dynon > starts in + and then goes down to -54 ???
- Sensor looks OK
- Ohmic resistance seems ot be good (measured: connected and not connected)
- Wiring seems to be OK (checked)

EGT
- Has been giving wrong values for a long time…
- It appears that a kind of... correct ambient temperature is indicated when the engine is “cold”
- When the engine is running, an incorrect value of approximately 385 ⁰C ..?
- Sensor looks OK
- Ohmic resistance is OK (measured connected and not connected)
- Wiring OK (checked)

• Connector strip behind panel, screws loosened and tightened again >> no effect
• Plugs in and out on the back of Dynon >> no effect
• Connector cleaned >> no effect

Other readings are ALL OK

I hope there are some ideas to fix this

THX!
Piet

 

[RVDan]

I am assuming a Lycoming engine. The CHT and EGT sensors are both thermocouples. They are voltage sources, and a resistance check is not valid. Also faulty thermocouples can act differently at different temps. What you are describing is typical of a bad thermocouple. That said, I would check the connections also. A faulty connection can also cause erratic operation. The voltages are in the range of single digit millivolts and resolution in the microvolt range and not measurable with any accuracy with a typical volt meter.