Glitch while logging from 34401A - Page 1
Forum section: electronics / testgear

author: kawal
author_rank: Frequent Contributor
timestamp: May 20, 2020, 01:14:20 pm
content: I been testing the logging capabilities of my setup and ran into what appears to be a glitch. The glitch has a repetitive nature. Is this normal for 34401A with a Auto zero on ?Could it be my setup (GPIB) ?Anyone seen this before?

author: Andy Watson
author_rank: Super Contributor
timestamp: May 20, 2020, 02:54:15 pm
content: Quote from: kawal on May 20, 2020, 01:14:20 pmHow are you reading the information ?I've seen similar problems caused by reading too quickly. Once you have requested say "voltage", you have to give the meter enough time to make the reading and transfer the value to the GPIB buffer. If you are too quick to read the value from the buffer you risk obtaining an invalid value from the buffer. Most of the time this does not matter because the buffer will contain a previous value that is near-enough. I believe the correct method is to request a voltage and then either check that meter has complete a reading or use the GPIB interupt system to flag that the buffer contains valid information. I usually fudge the issue by introducing a short delay between the request and the reading of the buffer.

author: kawal
author_rank: Frequent Contributor
timestamp: May 20, 2020, 03:57:47 pm
content: Quote from: Andy Watson on May 20, 2020, 02:54:15 pmReading via Agilent DMM_Connectivity_Utility_1.0.2.0 set for readings every 1s on average the readings are 1.46s over 10hours. Meter setup to manual 10V range, NPLC =10, Autozero ON.I dont think there is any option in the utility to add a delay between request and reading. But I assumed I am measuring so slow it will not be a factor.

author: Venturi962
author_rank: Regular Contributor
timestamp: May 20, 2020, 04:24:35 pm
content: To isolate the GPIB bus, can you try setting the NPLC to 0.02 (400us)? For reference, NPLC of 10 is 200ms.No experience with that Agilent application, but have used Python + PyVisa to continually poll for readings successfully. If you're comfortable writing code, this may be an option.

author: kawal
author_rank: Frequent Contributor
timestamp: May 20, 2020, 06:02:04 pm
content: The large glitch lasts almost 100 samples from the meter so pretty sure its not the communication but not 100% sure. The level of the voltage drop is very large at about 2mv .The small glitches are ~200uV and recover over 20 measurements.Lower NPLC will lower the resolution as well.

author: enut11
author_rank: Super Contributor
timestamp: May 20, 2020, 07:06:35 pm
content: I had a similar problem logging to the Agilent utility with my 34401A. Small glitches are to be expected but the large drop-out around the 13h mark was a surprise.

author: enut11
author_rank: Super Contributor
timestamp: May 20, 2020, 07:13:57 pm
content: While I was thinking about what might be wrong with the 34401A setup I happened to notice another log I did simultaneously using my 3456A on another computer.The same large dropout at the same time!I suspect it might be a power surge?

author: kawal
author_rank: Frequent Contributor
timestamp: May 20, 2020, 07:31:32 pm
content: Maybe the periodic drop is due to appliance like the air conditioner turning on?

author: kawal
author_rank: Frequent Contributor
timestamp: May 20, 2020, 07:59:00 pm
content: Quote from: enut11 on May 20, 2020, 07:13:57 pmBTW what tool are you using with the excel spreadsheet to log data?

author: myf
author_rank: Regular Contributor
timestamp: May 20, 2020, 08:55:46 pm
content: If you handle the battery in your hand for 1 minutes or 2, then its temperature increases, and tension varies about maybe 1%.Temperature has importance in long term measures.F.

author: Venturi962
author_rank: Regular Contributor
timestamp: May 20, 2020, 10:07:25 pm
content: Fun afternoon - here are 30K measurements with your settings (10 Volt Range, NPLC = 10) using GPIB & PyVisa on a 9 Volt Battery. Measurements take about ~0.4 seconds, so a reading every 1 second should be no problem.Command: multimeter.query('MEAS:VOLT:DC? 10, DEF')

author: kawal
author_rank: Frequent Contributor
timestamp: May 20, 2020, 11:05:28 pm
content: There was something funny with that battery . The battery was placed on carpet and no one touched it for days. The only thing about that battery was that it was old and maybe some chemical process going on. Changed to voltage source and looks good so far. I should know by later tonight if the problem is gone.

author: JohnPi
author_rank: Regular Contributor
timestamp: May 21, 2020, 02:13:36 am
content: Static building up on the carpet ? Is the outer case on a 9 V battery isolated from the terminals ?

author: enut11
author_rank: Super Contributor
timestamp: May 21, 2020, 05:20:37 am
content: Quote from: kawal on May 20, 2020, 07:59:00 pm@kawal, I am using the Agilent 82357B GPIB-USB hardware interface with the @bud modified XL logging program. The spreadsheet captures data and does real-time graphs.enut11

author: kawal
author_rank: Frequent Contributor
timestamp: May 21, 2020, 12:21:50 pm
content: Confirmed the issue no longer present - never thought a battery would cause an issue like this. I do not see it happening with a voltage source.

author: kawal
author_rank: Frequent Contributor
timestamp: May 22, 2020, 03:57:16 am
content: Here measuring 4.096V reference for 14H / 38000 samples - no more glitches