[...] One could look at the input current to a multimeter during an ohms-function overload, to see the PTC heat up and settle. [...]
....generally multimeters have a separate 10MOhm voltage input and a 10kOhm+PTC resistance/continuity input.
Keep those stories coming. We're here all night folks.
Especialy the low energy spikes will be hard to find any info about, because they don't cause imediate failure so it would be difficult to asess what would be the most common but already harmful energy and voltage level.But I think something well within Joes generators range.
You're going to have to define and quantify 'low energy' and fully specify the circuit characteristics and other test conditions for any further discussion to have meaning. I wouldn't call the jqsTM transients 'low energy'.
Here's two of them side by side:
....generally multimeters have a separate 10MOhm voltage input and a 10kOhm+PTC resistance/continuity input.
Keep those stories coming. We're here all night folks.
I found another meter that has a separate path for voltage that doesn't go via the surge resistor/PTC.
It's none other than our little friend the Fluke 101!
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The voltage input goes through R2/R3/R4/R5/R6/R7/R8. The Ohms/diode/continuity/etc. goes the other way.
See, I'm not crazy!
I haven't looked closely at this particular Uni-T but generally multimeters have a separate 10MOhm voltage input and a 10kOhm+PTC resistance/continuity input.
Here's two of them side by side:
So you have your choice of a CAT III/1000V meter with 600V fuses and quite a population of PTCs and MOVs or a CAT III/1000V meter with even less appropriate fuses and no MOVs. Let's call the versions 'fail' and 'didn't even try'.
....generally multimeters have a separate 10MOhm voltage input and a 10kOhm+PTC resistance/continuity input.
Keep those stories coming. We're here all night folks.
I found another meter that has a separate path for voltage that doesn't go via the surge resistor/PTC.
It's none other than our little friend the Fluke 101!
The voltage input goes through R2/R3/R4/R5/R6/R7/R8. The Ohms/diode/continuity/etc. goes the other way.
See, I'm not crazy!
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But then you have companies like Uni-T that have a reputation for changing and omitting parts in models on a whim.
...
That's anecdotal, and even though it matters for a company's reputation or "vibes", objectively you would have to comparatively test to see how it affects the product's performance or safety.
...
The surge resistor and PTC are still used in the voltage range to clamp via the two series MOVs to ground.
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The PTCs aren't on the "voltage measurement" part of a multimeter circuit, they're on the much lower-impedance "ohms/continuity/etc" part of the circuit.
...
But then you have companies like Uni-T that have a reputation for changing and omitting parts in models on a whim.
...
That's anecdotal, and even though it matters for a company's reputation or "vibes", objectively you would have to comparatively test to see how it affects the product's performance or safety.
Fungus posted this before, two UT-61E's.
I don't need a compartive test to tell me that one lacks all the MOV's and has smaller and lower rated fuses than the other.
EDIT: Here is my UT61E added to the right side:
And there are other examples of Uni-T meters doing this. I've even had it myself were a meter I have differs a lot from one someone else has.
(WTB I have not been following any argument in this thread, so I don't know the history here)
The surge resistor and PTC are still used in the voltage range to clamp via the two series MOVs to ground.
Once you have a clamp like for any main energy spike, then you don't need any major protection on the voltage input because of the attenuator. Maybe just a basic extra transistor clamp or something just in case.
EDIT: Here is my UT61E added to the right side:
The 10MOhms in that path will obviously attenuate a spike to the point where it can't damage the IC or it can be clamped by small components.
EDIT: Here is my UT61E added to the right side:That's three non-anecdotal variants!
Worse: You can see Uni-T deliberately planned to produce these unsafe variants after CAT certification by Intertek - the PCB has holes in it for different size fuse holders.
The surge resistor and PTC are still used in the voltage range to clamp via the two series MOVs to ground.No argument.
A few pages back I said something about the volts-measurement path inside meters not going via the surge resistor+PTC and I got called out for it. The 101 is an example of a well regarded meter that does exactly that.
The Fluke 28 is another example.
The Fluke 28 is another example. The 10M input resisotr is a ceramic jobbie, but in this case it does have an extra MOV on the other side of it.
The surge resistor and PTC are still used in the voltage range to clamp via the two series MOVs to ground.No argument.
What if the PTC heats up? Now the MOVs aren't doing much.
My only point was that many meters have a path from the input jack to the IC that doesn't go via the PTC as shown in your input protection video.
The PTCs aren't on the "voltage measurement" part of a multimeter circuit, they're on the much lower-impedance "ohms/continuity/etc" part of the circuit.
I haven't looked closely at this particular Uni-T but generally multimeters have a separate 10MOhm voltage input and a 10kOhm+PTC resistance/continuity input.
Which "UT61E" do you claim is certified? Which one do you think you'll get for 75 Euros? Better cross your fingers when you order...
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A) You removed the PTC and found the 101 could no longer read AC and/or DC voltages?
B) You removed the PTC and found the 101 could still read AC and/or DC voltages but you don't want me to eat too much crow?
C) You want to continue to believe your original statements and are concerned they are wrong?
D) Lack the soldering skills to lift one pin or the 101 costs too much and you are concerned about damaging it?
E) You're too lazy and can't be bothered to test your theory?
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A) You removed the PTC and found the 101 could no longer read AC and/or DC voltages?
B) You removed the PTC and found the 101 could still read AC and/or DC voltages but you don't want me to eat too much crow?
C) You want to continue to believe your original statements and are concerned they are wrong?
D) Lack the soldering skills to lift one pin or the 101 costs too much and you are concerned about damaging it?
E) You're too lazy and can't be bothered to test your theory?
Joe, you are assuming Fungus actually owns or has access to a Fluke 101. It's not that he is too lazy to test his theories, it's just that he can't. He really is the perfect armchair expert on DMMs that he has never even seen in person, much less taken apart.
How many Fluke meters do you own? 3 or so as I recall?
Five! (101, 187, 27FM, 37, 8060A)
Brymens? Only one!
The UT61E has been discontinued, so your entire argument is moot.
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But then you have companies like Uni-T that have a reputation for changing and omitting parts in models on a whim.
...
That's anecdotal, and even though it matters for a company's reputation or "vibes", objectively you would have to comparatively test to see how it affects the product's performance or safety.
Fungus posted this before, two UT-61E's.
I don't need a compartive test to tell me that one lacks all the MOV's and has smaller and lower rated fuses than the other.
EDIT: Here is my UT61E added to the right side:
And there are other examples of Uni-T meters doing this. I've even had it myself were a meter I have differs a lot from one someone else has.
The discussion evolves around safety and certifications. I don't know what the pass/fail criteria is for safety, only what I was told from two different companies that had very different interpretations. I assume all three flavors have been certified for use in CAT III 600 or what ever they are marked for. Is the cert worth anything? Personally, I have bad vibes about the whole process.
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But then you have companies like Uni-T that have a reputation for changing and omitting parts in models on a whim.
...
That's anecdotal, and even though it matters for a company's reputation or "vibes", objectively you would have to comparatively test to see how it affects the product's performance or safety.
Fungus posted this before, two UT-61E's.
I don't need a compartive test to tell me that one lacks all the MOV's and has smaller and lower rated fuses than the other.
EDIT: Here is my UT61E added to the right side:
...
And there are other examples of Uni-T meters doing this. I've even had it myself were a meter I have differs a lot from one someone else has.