Would be interesting to see what Agilent competitor have put into Keithley DMM7510.
From what I've heard, they have also added a temperature sensor near the front panel connectors for cold point compensation (for thermocouples). As there isn't one on the measurement board, my guess is that it is on the front panel next to the connectors. I don't suppose there is any chance you fancy taking the front panel off, is there?
I was kinda disappointed lookin g at the refernce board. The old 3458A had proper vihay foil resistors, these look like (probably still very good) thin film. Also the capacitors...
One glaring question I have is why did they use one of Nichicon's cheapest series for the two large filter capacitors? VR series are general purpose 85C parts which aren't long life, low ESR, or anything. Couldn't they have at least gone with some 105C rated VZ series parts since those would last longer? (Capacitor life doubles for every 10C below its rated temperature.)
I was kinda disappointed lookin g at the refernce board. The old 3458A had proper vihay foil resistors, these look like (probably still very good) thin film. Also the capacitors...
Why are people expecting the 34470A to match the metrology grade 3458A?
The 34470A is designed as a cheap-ish good value bench/system 7.5 digit meter in the TrueVolt range. It is not a replacement for the 3458A for metrology applications.
Why are people expecting the 34470A to match the metrology grade 3458A?
The 34470A is designed as a cheap-ish good value bench/system 7.5 digit meter in the TrueVolt range. It is not a replacement for the 3458A for metrology applications.
Some clever person out there will probably design a proper reference board that is a drop-in replacement for this design, which would make it perform closer to a 3458A, [but without the nifty "artifact calibration", which is one of my favorite features of the 3458A, and why I bought a 3458A and not a Fluke 8508A].
Some clever person out there will probably design a proper reference board that is a drop-in replacement for this design, which would make it perform closer to a 3458A, [but without the nifty "artifact calibration", which is one of my favorite features of the 3458A, and why I bought a 3458A and not a Fluke 8508A].Thanks for your great explanations.
What is the "artifact calibration" in the 3458A and why is it better than the Fluke 8508A.
Is the "artifact calibration" similar to the ACAL of the 34470A?
I'm guessing there is a 34480A coming, and they save all the possible improvement for that one. I'm actually not blaming the engineers for that, but it looks like the specifications were written by the marketing department.
The 3458A requires a 10V and a 10k reference only, to traceably calibrate nearly ALL ranges and modes. Its ultra linear (0.02ppm of range) A/D converter is the key element for that feature, unrivaled up-to-date. See hp journal 4/1989.
All other instruments, including the 8508A / 1281 require individual Cardinal Points for each range and each mode, instead. That sums up to about 40 different calibration values to be supplied to the instrument by a calibrator (Fluke 5720A) plus appropriate transfer standards, for correct TUR.
The 8508A / 1281 makes intensive use of Vishay BMF resistors, giving lower T.C. and higher timely stability than in the 3458A, and also got a more stable voltage reference, an LTZ1000 or an LTFLU at about 50°C , so most of the 90 days / 1 year stability parameters are better to a factor of 2-3 over the 3458A!
The 1kV DCV range in the 8508A features the usual power dissipation compensation, which the 3458A is lacking, that leads to mediocre 12ppm uncertainty at 1000V, compared to 2ppm for the 8508A.
By simply replacing these crucial components in the 3458A by better and actual ones, it would easily outperform the 8508A by far.
Frank
Thanks so much for this detailed information.
May be Keysight is working on a successor to the 3458A?
But Keysight would have to dig deeply into the software and hardware architecture of the 3458A, and I fear, they have got rid of many of the brains back then, so they simply lack Know How to make real improvements.
I repeat again: The 34470A is mostly a copy and paste device, no really new inventions here!
Do we seriously need to call it "Keysight", or can we just keep calling it HP or Agilent?
One glaring question I have is why did they use one of Nichicon's cheapest series for the two large filter capacitors? VR series are general purpose 85C parts which aren't long life, low ESR, or anything. Couldn't they have at least gone with some 105C rated VZ series parts since those would last longer? (Capacitor life doubles for every 10C below its rated temperature.)These high reliability devices are designed very conservatively, a proven part that has been used in designs with a long field record would be preferred over the modern equivalent even if there were some small theoretical improvement available. Shock testing and thermal cycling can be much more destructive on the tighter built capacitors and these environmental tests are the sorts of characteristics that are built into HP/Agilent/Keysight (and Tektronix) products that dont make it to the spec sheet.
Anyone noticed how the diode from the reference was also missing the diode in series with the heater? Or how Dave was showing the wrong page schematic for the negative reference?
Given all that it leaves freedom to voltnuts use own more stable LTZ1000 ref's in 34470A or even 34465A's Just design proper adapter connection and recalibrate unit.
Given all that it leaves freedom to voltnuts use own more stable LTZ1000 ref's in 34470A or even 34465A's Just design proper adapter connection and recalibrate unit.
i always hear that the units are not user caliberate-able ... or that is not true? ...
*waiting for continuation of video part 2?*