The solution for my issue is in this post.

https://forum.duet3d.com/topic/29608/the-problem-of-restoring-z-height-after-toolchanger-tool-change

2 commands in the tpost#.g.

I have defined the mesh point in the probePoint.csv file.
But the result looks not good. I think the magnets are so strong and interfere with the BLTouch when measuring.
So on, I need an inductive sensor.

I have now installed an inductive sensor. Unfortunately it doesn't work that way either.
The measurement stops above a magnet and this message appears.

Error: M280: Probe already triggered before probing move started.

What can I do?

I have defined the mesh point in the probePoint.csv file.
But the result looks not good. I think the magnets are so strong and interfere with the BLTouch when measuring.
So on, I need an inductive sensor.

@dc42
I haven't bought an inductive sensor yet. I can't find one, they're sold out everywhere.

But an idea is, of it is possible to define measuring points for the BLTouch so that I can find the position of the magnet and measure there and use this for the heightmap.

I'm using this external mosfet. If I use a different one, will the noise go away?
With Q50 the annoying sound is almost silent. Can I use it or will something break?

I want to test the F25 and became this message.

Fehler in Startdatei macro Zeile 69: exactly one of EFHJPSR must be given

M950 H0 C"bed" T0 F25

That sounds good, what I have to change it?

M307 H0 R0.475 K0.931:0.000 D7.84 E1.35 S1.00 B0

M308 S0 P"e0temp" Y"thermistor" T100000 B3950 C7.06e-8           	; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bed" T0                                        			; create bed heater output on bedheat and map it to sensor 0
M140 H0                                                  			; map heated bed to heater 0
M143 H0 S100								             			; set temperature limit for heater 0 to 100C 

ok. I'll order an inductive one and try it out and then report back.

Unfortunately, I have a problem with my Keenovo heating pad. I've just installed it. When I want to heat the bed to 60 degrees, everything is quiet up to 55 degrees. From 55 degrees onwards the heating pad makes noise. A humming noise that only stops when it's turned off.

Do you have any ideas? The heating pad is new.

For me, it is definitely the magnet. The BLTouch measures 4 positions perfectly. Then the magnet comes and the pin is not retracted and flashes blue and red. There are also neodymium magnets which are embedded in the plate from below.

Hi oliof,

I have the BLTouch in V3.1, so with a nylon pin. I think the mechanism doesn't work with the strong magnets.

Can you tell me a good inductive/scanning probe?

Hi everyone, I bought a new hotbed with magnets on the bottom. Unfortunately, the BLTouch doesn't measure properly. When it's over a magnet, it doesn't have enough power to pull the pin back and gives a message that the probe is in use.

What is a perfect alternative that works perfectly with magnets?