In the accuracy specifications for an AC voltage measurement with a Keysight 3458A, there is a distinction between source impedance of "50 Ohm" and "50 Ohm terminated" for the "flatness error including instrument loading" (the terminated situation has lower error). I'm confused about the difference between these. What makes 50 Ohm terminated or not? If I hook up a Keysight 33522B waveform generator to the 3458A with a BNC cable and a BNC to banana adaptor, which error is appropriate?
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\$\begingroup\$ You might need to link to all relevant text and diagrams in the manual for context. However, it sounds like the difference between a 50 ohm source via 50 ohms coax into a high impedance meter, and a 50 ohm source via 50 ohm coax into either a 50 ohm input on the meter, or an extra 50 ohm resistor in shunt with high impedance meter terminals. Either of the latter ways, the meter's high impedance is getting driven from 25 ohms. \$\endgroup\$Neil_UK– Neil_UK2024-05-10 15:28:21 +00:00Commented May 10, 2024 at 15:28
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\$\begingroup\$ @Neil_UK Thank you. The meter input is high impedance, the source output is 50 ohm, and there's just a BNC cable connecting them with no additional resistors/elements. So I'm just struggling to decide whether to call this terminated or not w.r.t. flatness error. The datasheet provides no additional diagrams or definitions, just a table of errors with "50 Ohm" in one row and "50 Ohm terminated" in another row under the heading "Source". I suppose I could just reach out to Keysight. \$\endgroup\$Gilbert– Gilbert2024-05-10 15:52:09 +00:00Commented May 10, 2024 at 15:52
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