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@ -18,7 +18,7 @@ To save the meter from an early demise, I replaced all the capacitors, and indee
Now that the meter seems to be working, I tried ACAL with the meter after letting it run, and now it shows me an error I have never seen before. error 204 flatness dac convergence 199. The error occurs while the meter is warming up and the ACAL step is always 100V. This immediately made me suspect the HV attenuation part, mainly the DAC. Cooling the board slightly, and seeing which component cooling makes it work, made me suspect U302, the LT318 op-amp behind the DAC. However, after replacing it with a different one, the problem still seemed to persist deterring me from assuming the fault is U302.
![amprep](3458-WorkLog/imgC.jpg)
Now, the resistors for this amp seemed to be affecting the pass or fail, replacing them and retrying indeed made the error disappear. Interestingly, looking at the circuit in question I would not intuitively expect this to fix the fault.
![resrep](3458-WorkLog/imgD.jpg)
![resrep](3458-WorkLog/imgD.png)
## Calibration
For calibration, the multimeter was first calibrated at home and then taken to a recently calibrated 3458A in another lab. Here the multimeter was adjusted relative to the calibration of the reference 3458A. Due to the erased calibration memory, SCAL was also required. This was done using an oscilloscope set up to measure RMS and a function generator feeding a signal to both. Is this good enough to meet the 3458A specifications? Certainly not in terms of amplitude adjustment, but it was good enough to get the self-test and start-up errors out of the way.