Products > Test Equipment
Vichy VC99 Multimeter Review and Teardown
johansen:
interesting, i edited my post, i've been using these things for 2 years and never noticed they are 6000 count lol.
i wonder if there is some way to modify the ohms scale for 1/10th the value. meaning boost the current source 10 fold.
johansen:
well i figured out how to multiply the 600 ohm and the 6000 ohm readings 10 fold.
and divide the 6000 volt range by ten.
There is a small problem of auto ranging does not work when the meter attempts to change the range between 6000 and 60,000 ohms.
Take resistor 25 in the datasheet which is connected to pin 21 of the chip and solder in a 112ohm resistor across it, to make it 100 ohms vice 1K
when you take the back of the meter off, you'll see a variable resistor accessible through a small hole in the board, in the top left corner next to what looks like a DIP-8, but its not a DIP-8, it is 4 resistors. you can measure them to identify them, as 1M, 100K, 10K and 1K, or you can take my word for it, (the bottom one is 1K. you'll need a 112 ohm resistor to make it 100 ohms.
I tried to use a 10 ohm resistor, but the meter is unstable, the "resolution*" means that you're going to be reading either 110 or 95 ohms, for a 1 ohm resistor. *remember we're dealing with microvolts here
Smokey:
--- Quote from: pascal_sweden on April 29, 2015, 12:18:27 am ---
--- Quote from: Amarbir[Lynx-India] on October 28, 2012, 05:07:20 pm ---Guys ,
Do Some of you share simons viewpoint ? ,BTW Simon i Have the Vichy VC97 Would Like To Give a Teardown Too .
--- End quote ---
What is the difference between Vichy VC97 and VC99? Is the VC97 good enough compared to the small improvement?
Any update on current measurement precision and autoscaling? Is it improved in VC97+?
--- End quote ---
The quick answer is that if you can't figure this stuff out it really won't matter.... and you probably will be better off not buying a crappy VCanything.
Smokey:
Is a turd with 10 flies on it an improvement on a turd with only 5 flies on it?
(And yes I know I posed positive stuff about these meters earlier in the thread, but I also acknowledged the turd-ness then too. Even turds are useful sometimes...)
pascal_sweden:
I found the specs for VC99 on DealExtreme.
Apparently it is 3 6/7 multimeter, with 6000 readings.
Still no backlight. Was hoping for the latter.
However I still have a question: if the highest number on the display is 5999.
How does this work out when measuring 1000V and what is the accuracy?
It is easy to understand for 600mV, 6V, 60V, 600V ranges, but how does it work out for the upper range between 600V and 1000V? How is that represented on the screen?
Other question: the precision of the multimeter is not only defined by the number of digits but also by the number of samples that are taken and averaged.
How do these meters perform here in relation to a real Fluke?
And what about the sample rate?
If I am correct, multimeters can be characterized by safety on inputs, sealing of housing to keep blast inside, number of digits, number of samples that are taken and averaged, and actual sampling rate.
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