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| Hioki RM3545 mini teardown |
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| gamalot:
Just a few pictures :) It's very easy to open the case, much easier than all my other instruments. The main processor is TI's LM3S5C31 (cortex-M3) |
| gamalot:
Analog board, the shield is also very easy to be removed :) It has a temperature measurement unit near the rear panel. |
| gamalot:
The main ADC is ADS1251, voltage ref is LT1027, and there is an AE resistor :) |
| lukier:
Some DC-DC converters in the top right corner. Maybe the AC-DC supply module provides only one voltage, earth mains referenced that goes to the digital board via the white cable and then the same output goes via the green cable to the DC-DC converters that provide isolation and analog voltages (bipolar supply etc). Then five TO-220 flapping in the breeze as Dave would say are perhaps LDOs to make the DC-DC outputs a bit more quiet. Interesting, I've always expected a transformer + linear supply, at least for the analog section, in precision instruments. Keithley's DMM7510 is a notable exception with its crazy coax transformer. Nice precision resistors around the analog board, with some AE 10K000 being the most prominent. ADS1251, hmm 19 effective bits, not really 6.5 digit, but almost. Something is crazy there. There seem to be 37 single channel optoisolators on the digital board alone (probably floating the signals on the big DB connector), and then 25 optoisolators on the analog board - crazy! Why not put MCU/CPLD on the floating side and just transfer some SPI over isolation barrier. Thanks again for the teardown, this is very interesting and unconventional design. |
| gamalot:
Main power supply is switch mode, and there are five 3-terminal regulator and filters after it :) |
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