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AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter
hughtmccullough:
So, those results show that improving the decoupling doesn't speed up the response when measuring resistance.
I tried measuring a 390 ohm resistor using the AN8008 and at the same time measured the voltage across the resistor using another meter. As soon as I connected the AN8008, the voltage across the resistor settled in less than one second to 32.60mV while the resistance value slowly converged towards 389.9 ohms. So, the reference current through the resistor clearly settles quickly and has a value in this case of about 0.085mA. That means the delay must be in the ADC measurement process. Now, if another meter can read the voltage quickly and it the AN8008 can measure other voltages quickly, why would there be such a lag in the resistance measurement?
kde:
--- Quote from: hughtmccullough on October 18, 2017, 07:34:12 pm ---That means the delay must be in the ADC measurement process. Now, if another meter can read the voltage quickly and it the AN8008 can measure other voltages quickly, why would there be such a lag in the resistance measurement?
--- End quote ---
What if they average several successive ADC readings to get the final value? Some kind of software LPF.
floobydust:
The DMM firmware has several digital filters with algorithm for the LCD displayed value.
If the input signal is moving around, the "fast" average is used.
Once the signal settles down, the "slow" average is used, for high accuracy. Takes a few seconds.
Both quantities are always being acquired, and the "slow" average" is primed (i.e. filter does not start from 0) by the "fast" value to speed response.
The "volatility" of the measured value determines which value to display. There is also hysteresis to avoid the LSD or rollover bouncing around.
It's one of the main reasons this meter has 9,999 count resolution - the firmware filters out a lot of A/D noise.
001:
NEW MODEL 8009 RELEASED JUST NOW :clap:
New tread here https://www.eevblog.com/forum/testgear/latest-aneng-9999-dmm-invented!-an8009-now!/
burkm:
The multi-million $ question is, is the new AN8009 just another model in the Aneng lineup or the successor to the AN8008, replacing it ?
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