| Weekly Health Check: WFI CCD #56 | 
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| Weekly Health Check: WFI CCD #56 |
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The detector system for scientific exposures is an array of 2x4 CCD44 chips by EEV which each have 2kx4k 15-micron pixels. Further details on the CCDs can be found in the WFI User Manual.
Derivatives
Standard CCD Test
Long CCD Test
The below plot shows the variation of the bias level, standard light-source (note that often a beta-light is used which, due to radioactive decay, will fade. It is also possible that the phosphor can be poisoned, but our data show no evidence for such an effect), gain, read-out noise, shutter error, and linearity error as a function of time. The values for the bias, gain and read-out noise are plotted along with the associated measurement error. The blue dashed line in the plots shows the mean value of all the points, while the dotted blue line shows the standard deviation of this distribution. The blue and red points in the bottom plot show the maximum deviations in a positive and negative sense wrt the least-squares fit of the linearity data. Plotted vertically on the bottom of the graph is the date (dd/mm) on which the test was made.
![[Click here to download ps file]](ST_deri.gif)
For printing, the above plot is also available in postscript format . The raw data can also be viewed in a tabular format.
Below we show the most recent test.
*** MIDAS logfile (05SEPpl1.3) *** Su, 24 Aug 2008 13:56:19 Page 1
*** MIDAS logfile (vers. 05SEPpl1.3) *** Su, 24 Aug 2008 13:56:37 Page 2
==========================================================
SUMMARY STANDARD TEST CCD#56 TAKEN ON 080824 IN norm MODE
==========================================================
BIAS
====
5 biases at start test: average = 128.43 stddev = 2.42
There were 0 hot pixels/columns detected
TRANSFER FUNCTION AND LINEARITY DATA
====================================
Table : Std_norm_56_080824
Sequence Exp_tim1 Med_cnt1 Med_cnt2 Variance Frc_cnt1 Frc_cnt2 el_adu1
-------- --------- --------- --------- --------- --------- --------- ---------
1 2.09 307.6 307.4 153.1 0.44 0.41 2.01
2 3.99 590.1 590.0 278.8 -0.03 -0.01 2.12
3 6.99 1031.2 1031.2 487.3 -0.70 -0.69 2.12
4 13.99 2067.1 2067.3 979.4 -0.84 -0.82 2.11
5 27.99 4143.4 4143.4 1963.3 -0.80 -0.79 2.11
6 41.99 6222.7 6221.8 2885.1 -0.73 -0.74 2.16
7 62.99 9352.8 9352.1 4421.8 -0.58 -0.58 2.12
8 83.99 12493.7 12492.7 5882.7 -0.41 -0.41 2.12
9 104.99 15646.5 15646.7 7325.4 -0.23 -0.23 2.14
10 139.99 20917.5 20918.0 9741.8 0.02 0.03 2.15
11 174.99 26223.4 26219.2 12225.6 0.31 0.29 2.14
12 219.99 33059.9 33058.5 15245.2 0.58 0.58 2.17
13 259.99 39165.8 39166.0 17888.2 0.82 0.83 2.19
14 299.99 45292.1 45292.2 20533.5 1.05 1.05 2.21
15 309.99 46828.6 46824.6 21537.8 1.10 1.10 2.17
-------- --------- --------- --------- --------- --------- --------- ---------
Dynamic range explored: from 673 to 102519 e-
Average count rate measured: 149 ADU/sec.
CONV. FACTOR AND RON
====================
C.Fact = 2.19 +/- 0.01 e-/ADU
RON = 5.29 +/- 0.02 e- RMS
SHUTTER ERROR
=============
Average shutter error derived from fractional count rate = -0.043 sec
LINEARITY ERROR
===============
Average linearity error after shutter correct. = + 1.10/-0.83 %
These errors represent maximum deviation in % from the average
*** MIDAS logfile (05SEPpl1.3) *** Su, 24 Aug 2008 13:56:37 Page 3
count rate after correction for shutter delay
In addition, the previous standard tests are available. Click in the table below to access these files.
| Standard Tests | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|