Products > Test Equipment
Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)
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joeqsmith:
I took a closer look at seeing if I could improve the serial port hardware.    It appears that while the receiver is interrupt driven, the transmit is polled.  The UART doesn't have any sort of FIFO and will set a flag when the byte is transferred to the serial register.  So their firmware is stuck polling this flag and sending one byte at a time.   Even if the hardware were improved, the firmware would have to be rewritten to support it.  The easiest thing if the firmware could be modified would be to change the polling time but I suspect that would cause more problems.   

Oh well.   I did add support to read and decode the status.   Shown with a 10Hz sinewave.   



joeqsmith:
Vishay 10k ohm foil resistor.  Using 4-wire mode.  Roughly 12 hours of data collected with the meter sitting out in the open.   Plotting the mean for the last 6 hours.   

https://www.mouser.com/datasheet/2/428/zseries-1022194.pdf
SilverSolder:
Looks good @joeqsmith!

Do you log temperature as well?  Could be interesting to see how that influences the meter.  I'm pretty sure they all behave differently!
joeqsmith:
I have a meat packing box that I use for temperature experiments but it's not large enough to place the meter into.   

I plan to restart the test with a lower value resistor.   If I measured the temperature, where would you think the most useful place would be to measure it? 

***
Looking through my stash, I thought I may have had a spare thermistor but no luck.  I do have one of those Fluke K-type adapters.   I could clip it next to the resistor with some foam to try and shield it from the air currents.   Not a great setup but better than nothing.   Let me know what you want to see.
dietert1:
As far as i understand, your test resistor drifted about 2 ppm. This is completely normal for those foil resistors. Sometimes you have to wait several days for those foil resistors to settle. You can see similar measurements here:

https://www.eevblog.com/forum/metrology/t-c-measurements-on-precision-resistors/msg2751598/#msg2751598

Regards, Dieter
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