PXI

cancel
Showing results for 
Search instead for 
Did you mean: 

PXIe-4080 impact of using 5 1/2 digit vs 6 1/2 digit setting

Solved!
Go to solution

Hi,

 

I am using a PXIe-4080 to do multiple DMM reads of multiple signals and I noticed that there is a noticeable difference in execution speed when programming the DMM to use 5 1/2 digits versus 6 1/2 digits. I put a basic VI together to try to benchmark the difference. With resolution set to 6 1/2 digits, 10 reads takes about 2.9s, whereas when setting to 5 1/2 digits, 10 reads only takes 46ms:

 

kbf_0-1633517090888.png

kbf_1-1633517135805.png

 

Is the 5 1/2 bit option actually working with 5 1/2 digit accuracy, or are other settings changing under the hood?

Why is there such a big difference in execution time between 6 1/2 digit and 5 1/2 digit options? The difference seems too big to attribute to the difference in required settling time.

 

Thanks in advance for the help!

 

0 Kudos
Message 1 of 4
(114 Views)
Solution
Accepted by topic author kbf

Part of getting more resolution is to average the reading over a longer period of time.


GCentral
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines
"Not that we are sufficient in ourselves to claim anything as coming from us, but our sufficiency is from God" - 2 Corinthians 3:5
0 Kudos
Message 2 of 4
(97 Views)
Solution
Accepted by topic author kbf

Yes, higher digits of resolution are always slow as it takes lots of averaging and calibration routines to get the additional digits of resolution.

 

This is documented in the Help file with the measurement default settings - https://zone.ni.com/reference/en-XX/help/370384V-01/dmm/408x_dmm_defaults/

santo_13_0-1633530743881.png

 

Based on the range used, the settling times also vary,

santo_13_1-1633530794454.png

 

Based on this information, it justifies the durations observed by you,

6 1/2 digits, 10 reads takes about 2.9s, whereas when setting to 5 1/2 digits, 10 reads only takes 46ms

 

You are free to adjust these settings to speed up measurement but the specifications of the instrument are based on this combination of settings, deviating from these settings will put you at an unknown accuracy spec.

 

 

 

 

-Santhosh
Semiconductor Validation & Production Test
Soliton Technologies
NI CLD, CTD
LabVIEW + TestStand + TestStand Semiconductor Module (2013 - 2020)
NI STS for Mixed signal and RF
Message 3 of 4
(81 Views)

Understood. Thanks for pointing me to that table in the documentation. That clarifies all the settings that are different between these two resolution settings.

0 Kudos
Message 4 of 4
(72 Views)