Strange Results From Switching Board Test


#1

Hi All,

I am just testing two new switching boards that I have installed and I’ve got some strange results.

The first 15 or so channels all seem to be functioning as desired with the measured/expected around 1. But all other channels on the boards measure around the 2.5-3 range of measured/expected. Any one got any ideas what may be causing this? There are no shorts or damaged channels from what I can see.

I have attached the pictures of the results:


#2

These results may still be ok. Typically, if a channel is not connected or a switch is malfunctioning, the corresponding channel will show a value very close to zero.

Some relevant points of note:

  1. The capacitors on the test board range across 3 orders of magnitude.
  2. To increase dynamic range in the feedback circuit, multiple feedback resistors are available and the appropriate feedback resistor is selected based on the impedance of the load being measure.
    The sharp step between the channel 15 and channel 16 on each board likely coincides with switching from one feedback resistor to another in the feedback circuit (see 2) due to a higher capacitor value associated with channel 16 (see 1).

Note that this step size is expected to decrease after reference load calibration and device load calibration are performed.

-Christian

···

On Tue, Aug 8, 2017 at 9:50 AM, Henry Bissell henryb...@gmail.com wrote:

Hi All,

I am just testing two new switching boards that I have installed and I’ve got some strange results.

The first 15 or so channels all seem to be functioning as desired with the measured/expected around 1. But all other channels on the boards measure around the 2.5-3 range of measured/expected. Any one got any ideas what may be causing this? There are no shorts or damaged channels from what I can see.

I have attached the pictures of the results:

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