Most kind, I'll try not to take you up on your offer though. Trouble is it's 2 senders so double the wire. I got 10m originally and to have the join out of the weather in the engine bay I used it all. First off I'll have a play about with what I have and/or some normal copper wiring as BusMonkey suggests.
@MorkC68 the "type j thermocouple extension wire" I bought from RS Components looks uncannily like a piece of cheap mains flex - blue brown doesn't comply with any thermocouple wiring colours. [Edit] Looked again, it's actually blue yellow with black sheath which is "old UK" colours for Type J extension cable. I have it all wired the right way round. I'm now thinking the meter is calibrated for the length of thermocouple wire supplied and that I should have used plain copper wire to extend as @theBusmonkey suggested. I have in effect outwitted myself, I should have bodged.
It does sound like it! or its the old british E type t/c cable. Anyway, we only have the one roll, it may have around 5m left on it. We will never use it!
Ah-ha - see edit above. I have no way to calibrate my gauge, so maybe as it works on the different resistance of different metals, the length of the wire supplied as part of the thermocouple is critical to the calibration. I've balls it up by extending with thermocouple wire. If you could calibrate, as you can, this would probably make for more accurate readings, but as i can't...
I've got a Dakota Digital CHT with the 18 foot sender cable - I don't remember anything about calibrating it and the gauge is sold for use with much shorter cables as well. The temperatures I see on the gauge are in the expected range.
So why isn't it reading properly on the original short wires when the thermocouple is in boiling water
Exactly - I'm doing it with a kit sold to 2CV owners with almost no documentation, "not suitable for certified aircraft" or somesuch. Cheap is the name of the game - I expect to have to fiddle a bit.
Here's my luddite solution: drive around for a bit and note the gauge readings borrow @Dicky 's hand held digi-mometer spot test the temps compare with gauge readings... I know it's not ideal, but it's better than nowt, for the meantime
But it reads F-all - it's MILES out. 350f is 175C or so - this one gets to 75 after drivng at 70mph for 20 minutes 70-75mph actually.
Yes, I don't think i need further confirmation of that. I'm not expecting accuracy, but it would be nice if the needles pointed around the centre of their sweep once it's properly warmed up.
http://www.csecables.com/technical-tables-useful-info/voltage-drop-calculations/ if the guage accuracy was good when tested vs boiling water with short leads, and assuming all is now connected properly, then maybe it is a voltage drop thing, or interference...have you tried shielded cable?
if you've got a half decent inductive multimeter, you could compare the output v close to the sensor, half way along the line and at the gauge, to rule it out
