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New UNI-T UT892 2000V AC/DC High Voltage Multimeter
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Kleinstein:
The live terminal is supposed to be for some non contact testing. Normally that function is more inside the case and not with a terminal.

The PTC for the high voltage input is odd: it would hardly help. I very much doubt it could withstand a higher voltage that chain if 2.5 M resistors. The main means of the protection are the resistors and they could have used more of those instead of the PTC. The PTCs are already a bit boarderline at 1000 V.

For the more normal meters there usually is a PTC (or multiple in series) for the protection of the ohms current source. There may also be one to protect the voltage sense path for the ohms function that can be shated with a mV function. The point here is that the function would go through the switch and there is a chance for arc over at the switch (or extra spac gaps) that may need extra protection. A decent CAT rating may want some protection for the case of arc over at the switch case, at least as a backup for transisents.
The big simplifcation from the extra terminal for just high voltage but no ohms is that the signal does not have to go through the switches.

There is some sense in not reusing the 10 M from the normal range: the normal range does have some connection to the switch for the ohms mode and this adds a little bit of leakage and capacitance. So A totally seprate chain of resistors makes sense for better accuracy and the resistors look relatively cheap, even if they would use 20x1 Meg instead.
Fungus:

--- Quote from: PartialDischarge on September 08, 2022, 05:35:25 pm ---
--- Quote from: Fungus on September 08, 2022, 05:20:43 pm ---I'd want a much higher input impedance for that.

--- End quote ---

CAT rating does not mean higher input impedance, it means higher clearance/creepage and higher power rating of passives.

--- End quote ---

I don't want it from a safety point of view, I want it from a measurement point of view. eg. Measuring the voltage at the output of a Cockroft-Walton generator can be delicate work.

Gyro:
It looks as if there would be sufficient space to insert a strip of insulating material down the side of the PCB, retained by the front and rear, to bolster the minimal isolation of the case flange. I think the 2.5M resistors are probably still above their element limiting voltage though.
PartialDischarge:

--- Quote from: Gyro on September 08, 2022, 06:46:50 pm ---It looks as if there would be sufficient space to insert a strip of insulating material down the side of the PCB, retained by the front and rear, to bolster the minimal isolation of the case flange. I think the 2.5M resistors are probably still above their element limiting voltage though.

--- End quote ---

The case has a big lip + the outer silicone cover. If you are worried about that I’d simply put silicone over the string. Also the mod that I did makes it safer since now there is 800kohm right after the jack.
Gyro:

--- Quote from: Fungus on September 08, 2022, 06:42:48 pm ---I don't want it from a safety point of view, I want it from a measurement point of view. eg. Measuring the voltage at the output of a Cockroft-Walton generator can be delicate work.

--- End quote ---

That's when it's a good time to build an external 100M+ divider (that's what we in the 20K Ohms-per-Volt club would do!)

[Edit: Yes, I know 20k OPV at 2kV is only 40M]
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