Cryoboard Noise

We are measuring noise on a 10 Kohm resistor in a single heater channel. This noise appears to be correlated with with FPGA dIn lines to the analog ADC.

Figure 1. Heater signal shown with clock (blue) and data In (pink) lines (U14, U17)
IC_U17_U14_pin6.png
Here we've triggered on U17.

Figure 2. The trace from the U17 isolator and the FPGA. The middle island is the PGND plane.
IsolatedSignalsCrossingPlanes.jpg

Figure 3. Heater signal shown with U17 data In (blue) and U18 Drdy (pink) digital lines.

There doesn't appear to be a correlation with the U18 digital lines and the heater signal.
U18_U17_trigU18_pin6.png

Figure 4. Heater signal shown with U17 data In (pink) and U23 data Out (blue)
U17_U23_trig_U17_pin6.png
The U23 lines appear to have some pick up when the heater/dIn lines toggle, as is seen by noise spikes in the blue trace. However, the U23 lines toggle at the right of the figure, and there doesn't appear to be any pickup in the heater or U14 lines.

Two possible explinations for the heater noise are:

1. The pickup is on PGND, the heater reference.

  • The digital lines or isolators could be where the coupling is taking place
  • However, the heater signal does not change when the analog/digital/heater powers are all the same (RHS2 shorted with resistor, J4 shorted to J11, power supply connected to P3)
2. The pickup is on the power lines.
  • The noise is still present when the heater switch is open. In this case measuring across the heater is only connected to PGND
Also note that there doesn't appear to be any pickup on the AGND (see Figures 3 and 4 below).

PGND variation

We've measured the variation in the heater ground across the board. Figure 6 shows the variation. The bottom trace connects the probes together (for reference), the second from the bottom is the PGND across the DB44 connector. The third from the bottom shows the voltage difference between channel 2 heater ground to PGND on C27 on the heater drive circuit (halfway across the board). The top trace shows the voltage difference from heater channel 2 PGND to the connector J11 where the power supply connects to the board. All traces are set to 500 mV per division.

Figure 5
PGND_cryorev2.png

April 28 2011

Recent bolometer noise tests have shown that when using the rev2 cryoboard, we rail our bolometer ADCs. Here, we look at psds of some bolometer raw dumps for different cryoboard set ups. For these tests, the analog, digital, and heater portions of the board are all powered separately.

Figure 6. Rev2 cryoboard with both heaters and thermometers.
rev2_153-w1_lowgain.png
Figure 7. Rev2 cryoboard plugged in, but not powered on
rev2_153-w1_pluggedin.png
Figure 8. Rev2 cryoboard powered on, but heaters not plugged in (RTD's plugged in) 153-w1.png
Figure 9. Rev2 cyoboard not plugged in
rev2_153-w1_notpluggedin.png
Figure 10. Rev2 cryoboard at high gain. ( There are some rails in the data )
rev1_153w0.png
Figure 11. Rev0 cryoboard at high gain.
rev0_153w0.png

Also, Matt noticed that measuring the voltage across a heater channel with a scope (using a resistor, not plugged into the dewar), looks similar to the raw dump data.

Figure12. Measuring across a 10kohm resistor on the rev2 board
heater_measurement_rev2_isogrounds.png
Figure 13. Measuring across a 10kohm resistor on the rev0 board
heater_measurement_rev0.png

With the table top board, we found that we saw this noise only when all three sections of the board are powered up (analog, digital, heaters).

Filter Boards

June 11 2011.

We measure bolometer dumps using the new filter boards. While the filter boards due reduce the noise in the rawdumps, they do not reduce them near their expected value. In all the following plots, the noise spike below 4 MHz is not related to the cryoboard, and occurs even when no thermometry/fridge controller is plugged into the cryostat.

no_filt_154_w3_gain1_rawdump.png no_filt_154_w3_gain1.png
Figure13: The rawdump timestream with no filter Figure14: The corresponding PSD

filt_154_w3_filt_gain1_rawdump.png filt_154_w3_filt_gain1.png
Figure15: The rawdump timestream when the filter board is used Figure16: The corresponding PSD

We have previously taken data with these filter boards. At that time the SENSE capacitors were too small and the DRIVE/SENSE combo was too strict to read the resistances. WIth that setup the filter boards were able to reduce the bolometer noise.

notherm_nofilt_154-w0rawdump.png notherm_nofilt_154-w0.png
Figure17: The rawdump for the unfiltered board (different gain than above) Figure18: The corresponding PSD

notherm_filt_154-w0rawdump.png notherm_filt_154-w0.png
Figure19: The rawdump for the filtered board Figure20: The corresponding PSD

Newest Filter Boards

Sept20_Filter_board_tests

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PNGpng 153-w1.png manage 46.5 K 2011-05-03 - 14:46 JamesKennedy  
PNGpng IC_U17_U14_pin6.png manage 47.0 K 2011-05-02 - 22:19 JamesKennedy  
JPEGjpg IsolatedSignalsCrossingPlanes.jpg manage 34.2 K 2011-05-02 - 22:20 JamesKennedy  
PNGpng PGND_cryorev2.png manage 22.9 K 2011-05-03 - 18:54 JamesKennedy  
PNGpng U17_U23_trigU23_pin6.png manage 29.5 K 2011-05-02 - 22:42 JamesKennedy  
PNGpng U17_U23_trig_U17_pin6.png manage 37.4 K 2011-05-02 - 22:31 JamesKennedy  
PNGpng U18_U17_trigU18_pin6.png manage 30.1 K 2011-05-02 - 22:19 JamesKennedy  
PNGpng filt_154_w3_filt_gain1.png manage 36.8 K 2011-06-12 - 05:22 JamesKennedy  
PNGpng filt_154_w3_filt_gain1_rawdump.png manage 45.9 K 2011-06-12 - 05:22 JamesKennedy  
PNGpng heater_measurement_rev0.png manage 28.1 K 2011-04-29 - 23:32 JamesKennedy  
PNGpng heater_measurement_rev2_isogrounds.png manage 28.6 K 2011-04-29 - 23:32 JamesKennedy  
PNGpng no_filt_154_w3_gain1.png manage 36.0 K 2011-06-12 - 05:26 JamesKennedy  
PNGpng no_filt_154_w3_gain1_rawdump.png manage 47.8 K 2011-06-12 - 05:22 JamesKennedy  
PNGpng nofilt_154_w3_filt_gain1.png manage 36.8 K 2011-06-12 - 05:07 JamesKennedy  
PNGpng nofilt_154_w3_filt_gain1_rawdump.png manage 45.9 K 2011-06-12 - 05:07 JamesKennedy  
PNGpng nofilt_154_w3_gain1_rawdump.png manage 47.8 K 2011-06-12 - 05:07 JamesKennedy  
PNGpng notherm_filt_154-w0.png manage 31.8 K 2011-06-12 - 05:07 JamesKennedy  
PNGpng notherm_filt_154-w0rawdump.png manage 46.3 K 2011-06-12 - 05:07 JamesKennedy  
PNGpng notherm_nofilt_154-w0.png manage 33.5 K 2011-06-12 - 05:13 JamesKennedy  
PNGpng notherm_nofilt_154-w0rawdump.png manage 47.1 K 2011-06-12 - 05:07 JamesKennedy  
PNGpng rev0_153w0.png manage 31.4 K 2011-04-29 - 23:36 JamesKennedy  
PNGpng rev1_153w0.png manage 43.0 K 2011-04-29 - 23:32 JamesKennedy  
PNGpng rev2_153-w1_lowgain.png manage 59.4 K 2011-04-29 - 23:36 JamesKennedy  
PNGpng rev2_153-w1_notpluggedin.png manage 40.2 K 2011-04-29 - 23:32 JamesKennedy  
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This topic: CryoElectronics > WebHome > Rev2_BolometerNoise Topic revision: r7 - 2011-09-20 - JamesKennedy
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