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Rms converter to match HP3400A?

ggabe

What is your suggestion to match the specs of the HP3400A AC millivoltmeter’s rms converter with analog parts available today? I’m drawing a line to exclude AD conversion and digital rms calculation. So it stays analog.

Below is the spec sheet:

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  • in reply to scottiebabe

    Two more lesser known facts about the 3400A:

    1. The input stage uses a miniature nuvistor tube. Seems reliable JFET solution was not available back in the days, when it was new in 1964.

    2. Chopper amplifier used CdS photo resistors + neon strobe lights to implement “fast” analog switches.

    The follow-on model, 3400B got a JFET replacement of the nuvistor, among many other modernization, like chopper stabilized opamp, and the bandwidth went up to 15MHz. Thermocouples stayed.

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