ok.. i understand...
ty.. and you are correct...
but, for all intents and purposes , where i live.. the ambient pressure will never reach of any substantial consequence to me..
so my 0 bar reading means that to me.. not that is 0,8 bar 0r 1.2 bar...
"Near Earth’s surface the pressure decreases with height at a rate of about 3.5 millibars for every 30 metres (100 feet)"
"Beacon Hill is the highest point in the English county of Norfolk. The hill is located 0.75 miles (1.2 km) south of the village of West Runton on the North Norfolk coast. At its summit the hill is 103 metres (338 ft) above sea level."
12 millibars is 0.012 Bar... or 1.2 kPa or just over one hundredth of my gauge scale.. 0 to 1 Bar..
i would need 100 millibars to move my scale above or stay below zero by one tenth. thats like diving down in air at atmospheric pressure 2800 feet? or climbing 2800 feet?
so even in very bad weather, or very good weather i dont think the .01 bar differences will greatly affect what i want to see... very low or very high readings at the wrong time.. it is far less than one tenth of a Bar... its around 100th of a bar, and pressure records show that... 1053 to @ 950 hPa...
so i am discounting atmospheric pressure completely.. i dont discount temperature and humidity, and i do have some idea from the ecu if it concerned about high temperature. the fans come on..
but i have a problem in sourcing the right sensors this mo..
"Good Morning -
Thank you for the email.
The pressure switch is primarily designed to be used in hydraulic systems where the working temperatures are lower than those experienced in an engine application.
On higher temperature applications we have to use a syphon system in order to protect the switch from the higher temperatures.
Therefore we don’t recommend the switch for application.
Technical Sales Engineer
ISIS FLUID CONTROL LTD
which is disappointing but not the end of considering other types...
oil pressure sensors are common and work typically 3 to 5 Bar switching point... assuming that ambient pressure is considered zero. its a consideration, they operate above 120 degrees C easily.
the higher pressure sensing isnt so easy to source yet.. but i am looking..
the other way to do it would be to use proximity sensors which operate at very small detecting distance... to see the gauge needle on my gauge. though its easy to source such detectors, making the electrical circuit to give me useful info, isnt easy.. since i would need several detectors, at the points i am interested in...
and i could plumb in the gauge permanently and see it too.. but that means changing the heater pipe connection to include pipe work for the gauge..
so if i can find pressure switches to do the job instead - its an easy solution..
anyone know of oil pressure sensors that switch above 0.8 Bar?
AND.. in reality i dont think this mo, that the pressure of the pump, even when the coolant is cold.. exceeds the pressure of the vent cap... else it would be venting all the time, pushing coolant out - and drawing in external air when the pressure drops... just like an unpressurised coolant system rad cap does.. remember those on cars? i used to have a pipe on mine into a bottle.. and when the engine cooled it drew the coolant back in... saved me topping up the rad all the time..
the F doesnt do that... unless the vent cap opens because of internal " vacuum" or internal high pressure.
i still think that knowing the pressure status is very valuable... even if i display it just with three leds.. and using two pressure sensing switches..
until i can source two switches my plan is to semi permanently plumb in the gauge to the header tank... and get some reasonable idea of the scale of the system in operation. Summer comes, and it will be interesting to see what happens on very hot days.. and the late summer thunderstorms.