Sonsivri

I'm looking at making a wireless resistance meter like my fluke233, But the trouble with the Fluke 233 meter the range is very short and intermittent dropping in/out.

I've made a wireless meter using an ESP32 using the esp-now protocol that can measure up to +/-100V DC only(that's all I need) and the range is very good.

But I now have the need to measure resistance wireless but need protection in case you accidentally use it in ohms range on a live circuit (upto +/-85V) like I can with the fluke meter without causing damage to it. It's an aid to find shorts in wiring looms where I measure the resistance between ground and the positive side of the cable which should read open circuit but in some places you move the loom and then this is where is could be damaged then sound bleeper and readings show on  a remote display(like the fluke meters) if the wires short or any resistance between them if it's not a short but drawing extra current and help trace the issue.

I've looked at the UT61E,fluke27,10 and 79 and some other schematics but can't get my head around how the range switch works and where the signals go or pick out the bits just for ohms part.
Not sure but I've looked at the Wheatstone Bridge  circuit ?

But not sure what's the best way or how to go about it ?
I've seen plenty of ESP32/Arduino circuits and that but they use the 3.3V/5V to feed the resistor then measure the voltage across the other one but this would blow if there was any voltage on the line and can only measure positive voltage. 

   

I know this is a bit off-topic. But if your goal is to work on fixing looms and not on designing a meter, how about trying a cheap bluetooth-enabled meter? Something like this perhaps:

https://www.aliexpress.com/item/1005004478341703.html?spm=a2g0o.productlist.main.1.1fcc6936gUbwt8&algo_pvid=dcb7db7b-1919-4a65-aecc-b85747b0e6df&algo_exp_id=dcb7db7b-1919-4a65-aecc-b85747b0e6df-0&pdp_npi=3%40dis%21CAD%2179.23%2137.24%21%21%21%21%21%40211bc2a016878865412112573d0744%2112000029303370709%21sea%21CA%21704753571&curPageLogUid=LHtnkvTV4naX (https://www.aliexpress.com/item/1005004478341703.html?spm=a2g0o.productlist.main.1.1fcc6936gUbwt8&algo_pvid=dcb7db7b-1919-4a65-aecc-b85747b0e6df&algo_exp_id=dcb7db7b-1919-4a65-aecc-b85747b0e6df-0&pdp_npi=3%40dis%21CAD%2179.23%2137.24%21%21%21%21%21%40211bc2a016878865412112573d0744%2112000029303370709%21sea%21CA%21704753571&curPageLogUid=LHtnkvTV4naX)

I like the challenge and it was just an idea, I got an owon bt35 meter but if what I remember the range was not to good on that either,.
Where I’m at the moment and considering using the m5stack so it can be used as a remote display as I came across someone that used it with an owon bt35 meter,

I’m trying to strip out the M5 stack part of the code so I can still use my existing wireless meter display and make it more simple.
This is the fun part about electronics is playing and leaning new things.
I've also been looking at the owon ow18e meter too.