Topic ID: id_16157937
Version: 1.0
Date: Jul 7, 2018 4:25:23 PM

Auto Test and Manual Test (16-Slice)

The difference between auto test and manual test is that the auto test feature runs a default number of iterations of each of the sub-tests, while the manual mode allows the user to specifically select a sub-test(s) and the number of iterations for that selection of test(s).

The following tests are executed during auto test:

1 DC CAL

This test is performed to check the absolute linearity and absolute counts of the DAS using DC CAL modes using various levels, Pre-Amp gains, and FPA gains. There are 15 stationary DAS scans taken, without x-ray. Each scan is analyzed for its absolute means count. This count range is different for each scan dependent on the injected dc signal. Then the ratio of the highest count scan to each of the other scans are performed, and are analyzed to a specific count range to determine the linearity of the FP amplifier.

If DC Cal fails and the failing channels are all on one board, then most likely that particular board is suspected bad. You can swap the board with a known good board and repeat the test.
If the failing channels are random and occur across many boards, then the problem may be a DAS Control Board (DCB) fault, or more likely, noise getting into the DAS. To correct for noise, ensure that the DAS air plenum is securely in place, and the fans are correctly mounted and orientated on the plenum. Also, check board seating, power supply noise, and cable seating on all DAS chassis.
It is also possible that the diagnostic feature of this test may be bad on the board. The charging capacitors on the converter board used to input the correct diagnostic signal into the front-end of the converter board may go bad. In this case, even if the diagnostic fails, there would be no adverse effect during patient or DDC scanning.

Table 1. DC Cal Test
SCAN #	DAS GAIN	PROTOCOL	DESCRIPTION
1	31	DCCAL 0	Used for Offset correction on all Gain 31 scans
2	31	DCCAL 8	FPA Gain 128 & all pre-amp caps.
3	31	DCCAL 1	Tests FPA = 1
4	31	DCCAL 2	Tests FPA = 1
5	31	DCCAL 3	Tests FPA =8
6	31	DCCAL 4	Tests FPA =8
7	31	DCCAL 5	Tests FPA =32
8	31	DCCAL 6	Tests FPA =32
9	31	DCCAL 7	Tests FPA =128
10	16	DCCAL 0	Used for Offset correction on Gain 16 Scan
11	16	DCCAL 1	Test Ext. Pre-amp Capacitor
12	15	DCCAL 0	Used for Offset correction on Gain 15 Scan
13	15	DCCAL 1	Tests all internal pre-amp Caps.
14	3	DCCAL 0	Used for Offset correction on Gain 3 Scan
15	3	DCCAL 1	Tests 9pf and 18pf capacitors

2 Offset Drift

A series of data collection scans, over a course of 120 seconds, and the offset means values are analyzed to measure the amount of variance over 120 seconds of scanning. There are three scans taken in a 16 x 0.625mm mode / Gain 3 and 3 scans in a 16 x 1.25mm mode / Gain 31 with a delay of 60 seconds between each scan. The absolute value of the Means are taken and compared. Scan time is 0.5 seconds @ 1640 views/sec

There should be little or no drift between the first scan of each scan mode and the scan taken 120 seconds later. The spec is ±3 counts for each channel across a 120 seconds time.

Table 2. Offset Drift Test
SCAN #	DAS GAIN	SCAN MODE	DESCRIPTION
1	3	16 x 0.625	Initial Offsets scan at specific technique
2	3	16 x 0.625	Offset scan after 60 second interscan
3	3	16 x 0.625	Offset scan after another 60 second interscan
4	31	16 x 1.25	Initial Offsets scan at specific technique
5	31	16 x 1.25	Offset scan after 60 second interscan
6	31	16 x 1.25	Offset scan after another 60 second interscan

Therefore, from Table 2 above, the difference in counts between scans 1 and 3 must be within 2 counts per channel, and also the difference in counts between scans 4 and 6. Failure analysis of the drift test may be a bad converter board, but also considerations need to be taken on account of room temperature fluctuations and DAS warm-up time. It may be normal for this test to fail if it is executed immediately after turning on the DAS.

3 Pop/Noise and Microphonics

A series of predefined rotating scans without x-ray, and the scan data saved on disk for analysis. The scan data is then view averaged and the standard deviations are measured against a spec limit.

This test takes a series of three scans. In the auto-mode, it takes ten iterations of the series. Failure analysis of this test is dependent on test results. Pop/Noise and microphonics issues can be caused by many system related conditions. Some of the most common could be the DAS/Detector interface (such as elastomer connection caused by dirt, oil, debris), flex top cover clamp torque incorrect, air plenum not installed, fan orientation not correct, power supply noise, electrical connections, gantry rotation/mechanical issues, and external influences.

It is highly important to look at patterns relative to DAS/Detector architecture, gantry rotation (azimuth position as well as velocity), and high voltage (with or without x-ray, rotor on/off).

Table 3. Microphonic Noise Scans
Scan #	Gantry Rotation	X-Ray	Rotor	Acquisition Mode	DAS Gain	Scan Time/VPS	Scan Data Analysis
1	Rotating	No X-Ray	On	16 x 0.625	3	0.5 / 1640*	Offset
2	Rotating	No X-Ray	On	16 X 1.25	31	0.5 / 1640*	Offset
3	Rotating	No X-Ray	On	16 x 0.625	3	0.5 / 1640*	Offset
4	Rotating	No X-Ray	On	16 X 1.25	31	0.5 / 1640*	Offset

note:

* For BrightSpeed Select Series product , Scan Time is 0.8s

4 Offset and Noise

This test collects DAS data with zero input current (no x-ray) and the mean value of each output channel is compared to spec. Also, the standard deviation is measured against a noise spec. It involves two scans, the first in a 4 x 5.00mm mode, gain of 31 and the other in a 8 x 1.25mm mode, gain 5. Refer to Table 4

Failure analysis is similar to that of DC Cal, with the exception that there is no input test voltage applied. Depending on failed pattern, based on DAS/Detector architecture, the fault may be a converter board, DAS/Detector interface, or power supply.

Table 4. Offset and Noise Scans
Scan #	Gantry Rotation	X-Ray	Rotor	Acquisition Mode	DAS Gain	Scan Time/VPS	Scan Data Analysis
1	Stationary 0° Deg.	No X-Ray	Off	16 x 0.625	3	1 / 984	Raw
2	Stationary 0° Deg.	No X-Ray	Off	16 X 1.25	31	1 / 984	Raw