User's Guide to CSC P0/P1 Cathode Electronics

S. Durkin , J. Hoftiezer , M. Johnson

June 1, 1995

OSU CAMAC GASPLEX/ADC Controller Module

Front Panel

Input - dual (twisted signal+ground) lemo cable signal input from gasplex board.

Offset - POT to control pedestal offsets.

Monitor - lemo output displaying signal to ADC offset voltage.

Channel - puts gasplex into single channel analog review mode.

Set Hold - puts gasplex into single channel analog review mode with voltage held at sample and hold time.

34-Pin Connector - control cable to gasplex board.

Test - not implimented.

No Shift - stops shift output of gasplex (experts only).

Delay - POT setting sample and hold time on gasplex chip.

Trigger - NIM input signal initiating gasplex sample and hold.

Reset - resets input control.

Test Pulse - not implimented.

Up-Down - Choose channel for analog review modes.

Display - Displays analog counter. See specific modes below.

The CAMAC gasplex/ADC controller performs the functions of: 1) sending sample and hold signals to the gasplex board, 2) readout control for the gasplex board, and 3) analog to digital conversion of the gasplex sample and hold analog signals. The ADC is 10 bits with a full scale of 1V. Along with standard running mode the CAMAC gasplex/ADC controller has several debugging modes set by front panel switches. These modes are described below.

With switches set in the nominal position the CAMAC gasplex/ADC controller will accept CAMAC commands. The display should read 7001 or 7001 <=> 0001 flashing. If you are having trouble read debugging.

One can view the analog output of the gasplex amplifier/shaper of any channel using this mode. Simply shift the sethold/channel switch into the channel position. Then push the up/down switch viewing the channel display to set a particular channel. An oscilliscope attached to the dual lemo input cable will then display the analog signal. If you have problems with this mode please contact the designer the CAMAC gasplex/ADC controller, Mark Johnson or else S. Durkin or J. Hoftiezer .

One can view the analog output of the gasplex amplifier/shaper of any channel using this mode. The difference here is that the analog signal remains constant after the sample and hold signal is received. This is useful for setting sample and hold timing as well as viewing the operation of the gasplex board. To set this mode simply shift the sethold/channel switch into the sethold postion. Then push the up/down switch viewing the channel display to set a particular channel. An oscilliscope attached to the dual lemo input cable will then display the analog signal. If you have problems with this mode please contact the the designer of the CAMAC gasplex/ADC controller, Mark Johnson ,or else S. Durkin or J. Hoftiezer .

The offset pot determines a DC offset of the input signal before it is digitized by the ADC. It can be monitored using a voltmeter attached to the monitor lemo on the front panel. One should set this pot so that nominal ADC pedestals read by CAMAC are on the order of 25 ADC counts. This should correspond to a monitor lemo level of about 640 mV.

The delay pot on the front of the CAMAC gasplex/ADC controller controls the sample and hold time on the gasplex board. This sampling time can be viewed direcly by using analog-hold mode and an oscilliscope (see above). It can also be viewed by looking at the track-hold signal (CLK_T/H, PIN 6 on the 34-pin connector) using an oscilliscope. The linearity of the amplifier depends strongly on this timing setting (see discussion below). It should not be set by maximizing the system gain since this timing leads to 15 percent nonlinearities in the amplifier. We find that the sample-hold signal should be set to 400 ns after the trigger.

These should normally be left alone. The dip switch controls the number of channels to read out and the readout speed. Since a 16 channel gasplex board and a 96 channel gasplex board exist, the dip switch settings need to be changed when changing board type. For any other changes call the engineer who designed the CAMAC gasplex/ADC controller, Mark Johnson .

OSU GASPLEX Board

Introduction

The gasplex chip designed by J. Santiard, CERN is the A.S.I.C. chip on this board that performs amplification/shaping as well as sample and hold. The OSU board provides power to the chips as well as interfaces the chip to the OSU CAMAC gasplex/ADC controller. Both 16 channel and 96 channel versions of the OSU board exist. It should be noted that the gasplex output is halved on output to match the 1 V ADC full scale of the CAMAC gasplex/ADC controller.

Requirements and Specifications

Power: +3.5 V (.2A) , -3.5 V (.3A), {current requirements for 96 channel boards}

Nominal Gain Gasplex: 10 mV/fC (fixed)

Nominal Gain System: 5 mV/fC or .5 ADC counts/fC (see below)

Noise: 4000 e's -> 3.5 ADC counts

The pedestals, gain, noise, and linearity of each channel were measured before shipping from OSU. A file of the nominal pedestals, gain, noise, and linearity for all channels are available along with a description of the measurement technique. In this process we found that the gasplex linearity depends strongly on the sampling time. Figure 1 shows this nonlinearity as a function of sampling time. As is seen in Figure 2 the best linearity (400 ns) is not obtained at maximum gain.