Products > Test Equipment
AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
Fungus:
--- Quote from: stj on July 16, 2017, 06:09:36 pm ---interesting thing in the manual for people who bitch about the fuses,
the maximum voltage for current readings is 36v DC or 25v AC.
--- End quote ---
...
--- Quote from: The Soulman on July 16, 2017, 09:05:02 pm ---It has everything to do with the voltage rating of the fuse, if the fuse fails the voltage that is across your supply now also is across the both ends of the fuse, just a couple of millimeters won't hold back a high-voltage.
--- End quote ---
Sure, but 37V isn't a high voltage. It's not going to jump that fuse.
FWIW most of those 10mmx3mm fuses are rated at 250V. In theory they'll stop 240V AC mains.
http://www.newark.com/c/circuit-protection/fuses-fuse-accessories/fuses/cartridge-fuses?fuse-size-metric=3.6mm-x-10mm
(not that I'd use this meter for mains work, and do we really have to keep laboring that point?)
Mark Hennessy:
--- Quote from: ocw on July 16, 2017, 08:39:18 pm ---
--- Quote ---Or to put it another way, what is wrong with what I'm doing?
--- End quote ---
I thought that my example made it obvious. Doing it your way both of my meters connected in series read about 47.4 mA. Doing it my way one meter reads 49.9 mA while the other reads 47.4 mA. It's clear which one is more accurate in measuring current when you do not want to go to the trouble of correcting for the meter's shunt resistance.
Let's say that my 5.00377 is a critical voltage supply which can't dip below 5.0 volts. Connecting the 34401A will lower the voltage to about 4.7658 volts while the AN8008 insertion will only cause the voltage to drop to 5.00227 volts.
While my expensive electrometers can measure current with insignificant insertion resistance (or burden voltage), my relatively inexpensive ADA4530-1 current to voltage converter can do the same thing. Because of that I want the manufacturers to start adding that feature in more moderately priced meters. If you shrug your shoulders and say that you are happy the way things are nothing will change.
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Yes, obviously, a current meter has a burden voltage (or resistance, if you prefer). And sometimes we have to take it into account... And yes, it would be lovely if manufacturers could minimise it somehow. I'm not shrugging my shoulders or otherwise; I'm simply not worrying about it right now because it's a completely different issue to the question of how closely a DUT meets its published specification for current accuracy.
To validate the manufacturer's specifications, you have to measure the way they did. So do you think they did what you're doing? I'm pretty sure that a DMM calibrator uses a current source for this, not a voltage source and low value resistor. Just a thought experiment: how about trying 1000V and 20k - what would that do for your numbers?
As I say, burden voltage, is quite separate from the basic accuracy as quoted in the spec. By all means complain about burden voltage - it's a noble cause - but you can't conflate the two ;)
I appreciate your time here, but in the context of reporting whether or not the AN8008 meets its specification, I think I'm happy with what I'm doing :-+
The Soulman:
--- Quote from: Fungus on July 16, 2017, 10:03:19 pm ---
--- Quote from: stj on July 16, 2017, 06:09:36 pm ---interesting thing in the manual for people who bitch about the fuses,
the maximum voltage for current readings is 36v DC or 25v AC.
--- End quote ---
...
--- Quote from: The Soulman on July 16, 2017, 09:05:02 pm ---It has everything to do with the voltage rating of the fuse, if the fuse fails the voltage that is across your supply now also is across the both ends of the fuse, just a couple of millimeters won't hold back a high-voltage.
--- End quote ---
Sure, but 37V isn't a high voltage. It's not going to jump that fuse.
FWIW most of those 10mmx3mm fuses are rated at 250V. In theory they'll stop 240V AC mains.
http://www.newark.com/c/circuit-protection/fuses-fuse-accessories/fuses/cartridge-fuses?fuse-size-metric=3.6mm-x-10mm
(not that I'd use this meter for mains work, and do we really have to keep laboring that point?)
--- End quote ---
There is a big difference between breaking ac or dc as ac (mains) inherently goes to o volts 100 or 120 times each second and therefore will remove the arc, after that there is enough space and material to prevent another arc-over.
DC on the other hand is much harder to brake, as the first arc doesn't die out by itself there is much more space and material needed to prevent it.
Also switches and relays have much lower dc than ac ratings.
I couldn't find a dc rating at all for the fuses you've linked to, not surprising as they are intended for ac mains only. :)
alm:
--- Quote from: boffin on July 16, 2017, 08:06:09 pm ---I'll probably pick up a couple of these as giveaways for my next course at work.
--- End quote ---
If you do that, at the very least put a label over the CAT ratings indicating not for use over 50 V or something like that.
MacMeter:
--- Quote from: joeqsmith on June 30, 2017, 11:28:39 pm ---The 8002 was pretty nice for the price. For low voltage, low energy it's way ahead of the free meters from HR.
Because it failed at a low enough level, it made it a prime candidate to run on my half cycle generator. Still not a lot of energy with this setup.
https://youtu.be/HrcxnbkkhYg?t=1793
--- End quote ---
That's the one I bought, the ZT102, same as the 8002. This 8008 looks good too for the price.
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