Proposed ALCT Tests


                   N. Bondar
                   N. Terentyev
                   T. Ferguson

                   October 31, 2002
 

I. Introduction

	The following proposal concerns making measurements on the analog part
    of the ALCT boards, which is used for the controls of the AFEBs.

	First of all, we would like to insure that the designed parameters of 
   the ALCT are realized for all three types of ALCT board.  To do this, we 
   will perform a set of detailed measurements, which are described below, on 
   one example of each of the three different types of ALCT boards - ALCT288, 
   ALCT384 and ALCT672.  We hope that the results will be the same for all 
   three types of ALCT boards, but the measurements will have to confirm this.  

	To make the measurements, one of each type ALCT board should be 
   installed on its corresponding type of chamber, along with all the rest of 
   the on-chamber electronics and cables.  The FAST site DAQ should be ON.  
   These measurements can be performed at the UF FAST site in a joint effort 
   between the ALCT and AFEB groups, with the assistance of a FAST site person.
   All results should be carefully documented.

        Based on the results of these measurements, and on previous information 
   from the FAST site tests and the ALCT production facility at UCLA, we will 
   then suggest a minimum set of relevant measurements to be made on the ALCT 
   calibration parameters and characteristics for EACH produced ALCT.  These 
   measurements would be done on the bench at the ACLT production site (UCLA).


II. Measurements at the UF FAST site

1. Reference voltage

	The reference voltage on the ALCT supplies the reference voltage for 
   all the DACs and the ADC on the ALCT with an accuracy of 0.1%.  We will 
   measure the reference voltage with a 5-digit voltmeter.

2. ADC calibration

	The threshold ADCs read back the actual voltage settings with an 
    accuracy of ~1.25 mV/count.  Changing the voltage settings with the DAC,
    we will measure the ADC vs. actual voltage setting dependence using a 
    voltmeter and the DAQ.   This will be done for each ADC on the ALCT 
    board.  The goal is to check the ADC linearity, confirm its calibration 
    (1.25 mV/count) and measure the ADC offset.  
	
3. Threshold DAC calibration

	The AFEB threshold is a function of the threshold voltage setting,
   which is provided by the ALCT threshold DAC with an accuracy of 
   ~5 mV/count.  However, the AFEB's input load can vary from board to 
   board, making the applied threshold voltage slightly different.
	
	We will measure for EACH DAC the threshold voltage vs. DAC code 
   dependence.   We will use the DAQ and the calibration of the ADCs 
   described above to set up the DACs and to read back the ADCs.  The 
   goals are to confirm the DAC's calibration (5 mV/count) and to measure 
   the DAC offsets (with and without the AFEBs, in order to see if there
   is a difference).

4. Test pulse generator calibration procedure

        We will perform the following test procedure on the test pulse
   generator on the ALCT board.

    4.1 Measure the parasitic test pulse maximum amplitude on each AFEB 
        when the ALCT pulse generator is in the "OFF" mode (pulse 
        generator -off, test pulse buffer -off, ALCT is running). It 
        should be zero.
	
    4.2 Increase the amplitude of the test signal (by using the DAC) to 
        measure the maximum amplitude.  Measure the pulse shape at the 
        ALCT output point and at the AFEB input point for each DAC code 
        setting.  These measurements should be done for each AFEB and for
        each corresponding ALCT output.
	
    4.3 Repeat the procedure in 4.2 for all 6 test strip outputs of the 
        ALCT generator on the chamber.  This measurement is a 
        chamber-dependent issue and the results can vary for different 
        types of ALCT.  So we will repeat the measurement using the 
        three different types of ALCT board.

	The tools for making the measurements described above (4.1-4.3) 
    are a digital scope with "a trace storing option" and the DAQ.  The 
    pulse shape traces should be saved into files.  Note that a 
    measurement with an oscilloscope is a "person-dependent" procedure.  
    Therefore, it is important that the test conditions be defined as 
    precisely as possible.

	The goals of the above measurements (4.2-4.3) are to calibrate the 
    test pulse amplitude vs. DAC dependences, and to measure the linearity 
    and the offsets.

5. ALCT generated digital noise level

	The ALCT digital noise determines the minimum stable AFEB threshold
    setting.  This noise level is an important part of the ALCT performance, 
    as well as a measure of the quality of the ALCT grounding and shielding.
    We will measure the analog and digital noise by performing the following 
    procedure.

    5.1 With an oscilloscope, measure the AFEB noise using the AFEB test 
        channel, both with the DAQ stopped and the DAQ running. The number 
        of AFEBs to be measured and their location on the chamber has to 
        be determined.  

    5.2 Measure the analog noise and the crosstalk with the DAQ (same as the 
        FAST site tests 13,14) to see any difference between the three 
        types of ALCT.