critical adjustment

[Alexismex]

Hello Carl,
I have a technical question , if you can help me , it is important for me to know because you have many more experience in
making boards and many metal detector...to help me
My question is :
There is some difference in this trimmers , this ones , like you use in your TDI ...a one turn trimmer and the 10 multiturn trimmer like the blue in the photo...some difference in the durability to sustain the adjustment in time and in vibration process...
it is better to use the trimmers like you use in TDI ... i don't think you use it for the price in the Tdi because it is almost the same ....
I see also many times ...this type of trimmers (the brown color) in oscilloscope this is a reason to use it in the place to use multitun trimmers which are more easy to adjust ?????
My question seems simple and silly !!! but i did have some problem in my home made detector with critical adjustment with multiturn 10 trimmers (quality bourns etc...) when i adjust in my home city town at 2000 meters above the sea and when i check my preset at sea level o with many vibrations process ...the multiturn moves (i barnish it) !!!! and the detector desadjust....
Also i try to use the more fixed resistor but sometimes it is necessary use trimmers like i see many's in the TDI ..
Thank you for your help and knowledge ,
Have a good time , it give me pleasure to see you in the video
Saludos
Alexis

[Alexismex]

hello forum , nobody answer
please tell me if you have experimented some difference to stay in the precise first adjustment between this two type of trimmers .....

o perhaps i did not explain me well ...
i have repair many metal detectors and many time the problem is the misadjustment of some trimmers,,,(loose adjustment)
The same for two new metal detector ...sometimes they are well calibrated in the lab of some company and when the arrived at Kel.... they vary a lot between the two unit in depth.... sometimes they loose a little calibration because of the transportation (vibration...etc...)
and i did not speak... when this same metal detector travel from US to a foreign country ..... miles of vibrations , changes of temperature and change from sea level to mountain etc......

What is your thinking????

[Qiaozhi]

Personally, I always use multi-turn pots, but if the adjustment is not critical then single-turn pots should be ok.

[mikebg]

Saludos Alexis!
Amateur radio designers also prefer multi-turn trimmers for portable equipment because of their better hermetisation. For best hermetisation they put one drop of lubricant in the spindle head as shown by the arrow.

[Alexismex]

Thank you Qiaozhi and Mikebg for the tip ,
good day for you
Alexis.