Products > Test Equipment

Brymen BM789

<< < (34/81) > >>

joeqsmith:

--- Quote from: Fungus on September 19, 2021, 02:48:32 pm ---
--- Quote from: joeqsmith on September 19, 2021, 02:28:27 pm ---The last video shows me shorting the leads after applying a kV to meter in an attempt to look at the current.   Maybe that's how they design them in Canada.  floobydust would need to provide a brand/model for one that can be damaged as they suggest.      If I have the meter, I would certainly be willing to attempt to replicate their findings.   

--- End quote ---

Surely the stress of discharging it is no worse than the stress of charging it.

(assuming a low source impedence for charging).

--- End quote ---

Considering the attached schematic, assuming V+ is 12V, D is a silicon diode,  R is 10kohms, C is 10uF and all components are perfect (no parasitics,  switch resistances are zero when closed and infinite when open), under what condition will the current through the capacitor reach it's highest peak current?

A) when charging
B) when discharging
C) A and C
D) non of the above
E) what's a diode?

Fungus:

--- Quote from: joeqsmith on September 19, 2021, 03:17:15 pm ---Considering the attached schematic, assuming V+ is 12V, D is a silicon diode,  R is 10kohms, C is 10uF and all components are perfect (no parasitics,  switch resistances are zero when closed and infinite when open), under what condition will the current through the capacitor reach it's highest peak current?

--- End quote ---

Does current flow through a capacitor?  >:D


--- Quote from: joeqsmith on September 19, 2021, 03:17:15 pm ---A) when charging
B) when discharging
C) A and C
D) non of the above
E) what's a diode?

--- End quote ---

Assuming you meant the peak current flowing at point "I" in the circuit, I'm gonna go with (A)

joeqsmith:

--- Quote from: Fungus on September 19, 2021, 03:46:48 pm ---
--- Quote from: joeqsmith on September 19, 2021, 03:17:15 pm ---Considering the attached schematic, assuming V+ is 12V, D is a silicon diode,  R is 10kohms, C is 10uF and all components are perfect (no parasitics,  switch resistances are zero when closed and infinite when open), under what condition will the current through the capacitor reach it's highest peak current?

--- End quote ---

Does current flow through a capacitor?  >:D


--- Quote from: joeqsmith on September 19, 2021, 03:17:15 pm ---A) when charging
B) when discharging
C) A and C
D) non of the above
E) what's a diode?

--- End quote ---

Assuming you meant the peak current flowing at point "I" in the circuit, I'm gonna go with (A)

--- End quote ---
First hit on displacement current gives us wiki:
https://en.wikipedia.org/wiki/Displacement_current

For the meters, I would assume that the charge/discharge would be basically the same.  Even on the 189, it looks like it follows two different paths.  Still the difference is  negligible.   Still, it's common to find exceptions when making blanket statements. 

Fungus:

--- Quote from: joeqsmith on September 19, 2021, 04:02:10 pm ---For the meters, I would assume that the charge/discharge would be basically the same.  Even on the 189, it looks like it follows two different paths.  Still the difference is  negligible.   Still, it's common to find exceptions when making blanket statements.

--- End quote ---

It's hard to imagine a measuring device that would want the capacitor to discharge faster than it charges. It would go horribly wrong as the AC frequency increases.

bdunham7:

--- Quote from: 2N3055 on September 19, 2021, 06:32:37 am ---Well if you put, like I suggested (also repetitively) other meter in set in ohms to input of the meter in question, you will see if input impedance going high, to isolation range. Also, you can take a meter in question, and exactly what was said: you charge meter input wit, say 12V to be safe and discharge it into scope probe set to safe range. If you see exponential decay, there you are you have capacitance.

Also, there is only one way to do it, really. So AC coupled, in this context, means serial capacitor...

--- End quote ---

I don't have this meter to test, so until Caliaxy and joeqsmith posted, I had no way of knowing what this result would be.

There is not only one way to do it, this I know because I have examples where it was not done in exactly the same way.  The F116, for example, passes the HV blocking test even on the lowest (non-mV) range of 6.000V.  However, its measured input resistance (DC) is 10M on all ranges.  This is an issue of some significance to me because I'm using HV divider probes to measure HV at times and I've always wanted better results.  Depending on the divider probe, you could end up charging a blocking cap to the full HVDC bias, which would be bad--so you would avoid using a truly AC-coupled range with an HV probe that didn't have a lower divider resistor.  Fortunately most of them DO have  this lower divider, but I did have one go open. 

So I'm still learning tidbits here and there that I haven't thought of.  The F116 is fairly new to me, and I hadn't considered the input characteristics beyond knowing that the AC input had a 10M straight resistance across it.  Only with this thread did I discover that the mVAC range is actually only mVAC+DC.  Now I know that the F116 also eliminates the hazards of a charged AC blocking capacitor, since the 10M across the front end will quickly discharge it.  I'm not saying that Fluke did this deliberately to prevent HVAC technicians from frying control circuitry, since that might be an " embarrassing fanboy apologist fantasy", but it is a characteristic.  Interestingly, they seem to have done this by using a 10M capacitive coupled input in parallel with a 10M resistor across the front end, giving the meter an effective input impedance of 5M on the AC ranges.  That does actually seem deliberate.   And it messes up my 80k-40 HV probe by 10% or so...

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod