Here's a 3-hour test comparing the DAQ6510 (same analog board as DMM6500) and my SDM3065X. Both had hours of warmup time. Both were set to 10PLC. Everything I could set the same, I did.
The Siglent appeared more stable*, but also more susceptible to environmental change. By the end of the test, my office wasn't just colder, the humidity dropped to 26%. Gross.
The DAQ was less susceptible to environmental change, but was slightly further off from the expected ref value.
Last cal for the DAQ6510 was in April 2024. SDM3065X was September 2023.
Overall, neither of them suck. 😉
Thanks,
Josh
*I found the setting, the DAQ was sampling too fast. I'll eventually do another test with the slower sample rate.
ETA: The SDM3065X is my loudest DMM. The DAQ is much quieter.