Author Topic: Keithley DMM6500 ADC workings  (Read 941 times)

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Offline JelbertTopic starter

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Keithley DMM6500 ADC workings
« on: April 27, 2022, 10:05:26 pm »
Hi,

I'm planning to buy a new dmm and the Keithley DMM6500 looks perfect. When I read the datasheet it tells about a 16 bit ADC used in the scanning mode. An 16 bit ADC is not accurate enough to achieve a 6 1/2 digit readout. So how does this dmm work?
I asked at tek and the local distributor answered by sending the datasheet and not explaining at all. So how does it work? A dual slope ADC next to the faster ADC for fast scanning or only the ADC and some math interpolation trick? 
 

Offline TiN

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Re: Keithley DMM6500 ADC workings
« Reply #1 on: April 27, 2022, 10:36:24 pm »
16 bit ADC is used for sampling/digitize function, while MS ADC used for 6.5-digit readings and normal operation.
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Offline bdunham7

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Re: Keithley DMM6500 ADC workings
« Reply #2 on: April 27, 2022, 11:02:10 pm »
When I read the datasheet it tells about a 16 bit ADC used in the scanning mode.

I think you have the terms a bit crossed.  The DMM6500 can take an optional multi-channel scanning card that lets it take readings from multiple inputs in sequence.  That is 'scanning'.  It would typically use the normal ADC--multislope with autozero--for that function, the same is it would for any normal reading.  The 16-bit ADC is for the high sample rate digitizing feature where IIRC it can take something like 1 million readings per second, but obviously with only 16-bit resolution.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline JelbertTopic starter

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Re: Keithley DMM6500 ADC workings
« Reply #3 on: April 28, 2022, 04:43:02 am »
Thank you both,
I'm going to order this device. Yes I had the terms a bit crossed.
 


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