Understanding the 1830A Compensation Modes

For users of 1830A DC Substitution RF Power Meter
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csperrazza
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Joined: Tue Oct 21, 2008 2:23 pm

Understanding the 1830A Compensation Modes

Post by csperrazza »

The TEGAM 1830A is two separate isolated bridge balancers and voltmeters. These are allocated as "Channel 1" = "RF Bead Balancer", and "Channel 2" = "Compensating Bead Balancer". The names have significance in the context of HP-style co-axial thermistor mounts with auxiliary thermistor beads for environmental temperature compensation. The three modes use the two channels differently:

432 Compatible Mode assumes that a temperature-compensated mount is attached. The diagnostic and error checking routines monitor both channels for errors, and the voltmeter readings from both channels are combined using the same equation that appears in the HP432 manual for making compensated power measurements using external voltmeters. This mode introduces the uncertainty and noise of two channels, but can compensate for significant environmental swings. This is not a recommended mode for a standards lab but can be useful in areas with less tight environmental control.

432 Bias Mode assumes that a temperature-compensated mount is attached.
The diagnostic and error checking routines monitor both channels for errors, and the voltmeter readings from only Channel 1 are used in the simple power equation of P=(V[1]^2 - V[0]^2)/R. This method is recommended for standards lab use with 478, 486, 8478 series thermistor mounts, because the errors from only one channel are transferred, While in a lab the mount environment can be stabilized using insulation.

None Mode is for use when a mount without compensating beads is used. A TEGAM or Weinschel mount is an example of this type. Using "None" mode prevents the unbalanced Channel 2 from causing error messages. None mode uses the same power equation as "432 Bias" mode.

These modes only impact the "Calibrated RF Power" reading. On the Screen that shows both "RF Power" and "Comp Power" these are the power changes since the last Zero of Channel 1 and Channel 2, respectively. The 432 Comp equation is ROUGHLY RF Power - Comp Power.

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