Logo Caen

DAQ & trigger units

ADC Conversion Time
The time required, after the sample command, to digitize the analog signal

ADC Dead Time
The minimum amount of time required after the end of a GATE to have the ADC ready for a new acquisition

ADC Resolution
The number of bits in which the ADC full scale range is divided

Address Modifier
It is the code which carries the information about the size and the type of VME data transfer

Analog Adder
A linear Fan-In

Logical designation or circuit function meaning that all inputs must be in the TRUE state for a TRUE output

An input signal which suppresses the normal functioning of the unit for the duration of its application

A monolitic, multilayer printed circuit board at the rear of a crate providing bus dataway, power lines and modules’ connectors

The frequency range over which the gain of an amplifier or other circuit does not vary by more than 3 dB

Baseline Restorer
A circuit that maintains the amplifier DC output (baseline) at fixed potential independently from counting rate

Baseline Shift
Drift of the amplifier DC level (baseline) that may impair the peak amplitude stability

Block Transfer (BLT32)
A 32 bit VME data transfer from/to a series of adjacent locations of a module

Bridged Outputs
Parallel output connections which share the same driver

Computer Automated Measurement And Control; international standard of modular instrumentation defined by the ESONE Committee of the JNRC (document EUR4100e, 1969 and subsequent revisions); CAMAC One single-width unit, as per IEEE Standard 583, has 305 mm x 182.9 mm x 17 mm overall dimensions.
They can, however, also be built in multiples of this standard, that is, double-width, triple-width etc.

Controlled Area Network; network consisting of multiple microcontrollers that need to communicate with each other

Chained Block Transfer CBLT
Sequential read out of multiple VME slave modules selected by a single address cycle

Charge ADC
An ADC which measures the input charge integrated during the GATE period

Charge Sensitive Preamplifier
A preamplifier whose peak output amplitude is directly proportional to the input integrated charge

Coincidence Unit
A device which performs the AND logic function of two or more inputs

Common Mode Range
The maximum range (usually voltage) within which differential inputs can operate without a loss of accuracy

Common Mode Rejection Ratio
The ratio between the common mode input noise and the output voltage, expressed in dB. It expresses the ability to reject the common mode noise

Common Mode Noise
The noise which appears equally, and in phase, on the IN+ and IN- nodes of a differential input with respect to ground

Common Start
A signal common to all input ch. which marks the beginning of a time interval measurement in a TDC

Common Stop
A signal common to all input ch. which marks the end of a time interval measurement in a TDC

Complementary Output
A logical signal with its FALSE state and TRUE state reversed from that of the normal output signal

Constant Fraction Discriminator
A discriminator which allows to minimize time walk errors encountered triggering constant rise time and varying amplitude signals

Control and Status Register (CSR Space)
A register used to control the operation of a device and/or record the status of an operation. Its allocation and usage is part of the VME specification

Unwanted coupling of a signal from one channel to another one

Daisy Chain
Connection of control signals on several boards in a chain

DC Level Shift
A programmable DC Offset

Differential Input
A circuit that is sensitive to the algebraic difference between the IN+ and IN- input signals

Differential Non-Linearity
The maximum deviation of the ADC bin widths from a flat distribution (expressed as %)

Differential Output
A circuit with two outputs that have equal but opposite signal excursions around a fixed potential (called the common mode level)

Double Pulse Resolution (DPR)
The minimum pulse pair resolving time (measured between leading edges of the incoming pulses)

Dual Port Memory
A memory module which has two interfaces through which data can be transferred

Dwell Time
The trigger generation period of the internal programmable timer of a MultiChannel Scaler

Emitter-coupled logic, an unsatured logic performed by emitter-coupled transistor. Normal ECL LOGICAL 0 = LOW = -1.75 V and LOGICAL 1 = HIGH = -0.9 V

Event Counter
A counter which indicates the number of trigger signals that a DAQ module has processed

Fall time
The time required for a pulse to decrease from 90% to 10% of full amplitude.

The mixing of more than one input to obtain one of the following outputs:
Linear > the algebraic sum of the inputs
Logic > the logical OR of the inputs

The reproduction of an input signal on more than one output

Full Width at Half Maximum, the width of a pulse or waveform at 50% amplitude

An input control signal used to enable the passage of other signals

Geographical Addressing
Addressing of a module according to its physical location (the slot number) in a crate

Ground Loop
A low impedance path along which voltage drops occur due to external pick-up

High Speed CAENET
A CAEN proprietary 1 Megabit/second serial transmission protocol

A signal or switch which prevents a unit from operating or responding to inputs

Integral Non-Linearity
Maximum deviation (expressed as fraction of full scale) of ADC response from a straight line fit

Interchannel Isolation
Cross talk rejection ability

I/O Register
A device capable of either receiving or sending a pattern of logical signals

In a VME V430 compliant backplane, a 3 row, 30 pin connector (jack) providing “2 V, -5 V” (useful to supply ECL electronics without the need of on-board DC-DC converters) and ±15 V power lines, geographical address lines (SN1-5) and some User defined lines (CK, SG, CL)

Memory register

Latching Scaler
A scaler where the counters can be latched “on the fly” without interfering on data acquisition process

Leading Edge Discriminator
A device that delivers, for each input signal that is larger than a programmable threshold, a logic pulse

Live Insertion
The possibility of inserting (or removing) a board into the crate without switching it off

Low Threshold Discriminator
A Leading Edge Discriminator with high sensitivity on small signals

Least Significant Bit

Low Voltage Differential Signaling (specified in the IEEE 1596.3 standard), it’s a way to communicate data using a very low voltage swing (about 350 mV) over balanced connections

Majority Logic
Generates a TRUE output when the number of coincident inputs is equal to or greater than some specified threshold

A device which is capable of controlling the data transfer operation according to some protocol

Multiplexed BLT; it is a data cycle similar to the BLT, but it transfers 64 bit words instead of 32 bit ones

Multicast Mode MCST
Multicast (MCST) Mode allows commands to be sent to chosen set of VME slave modules in only one data transfer bus transaction

Multichannel Scaler
A scaler provided with a number of independent channels and a periodical programmable trigger, that allows to record counting rate as a function of time

Multievent Buffer
A FIFO-like buffer where it is possible store/read the data belonging to multiple triggers

Multihit TDC
A TDC that can accept multiple hits per channel

A complementary output AND circuit

Nuclear Instrumentation Module, international standard of modular instrumentation defined by U.S. NIM Committee (AEC Report TID-20893); NIM modules must have a minimum standard width of 1.35 inches (3.43 cm), a height of 8.75 inches (22.225 cm) and a 10 inches depth (25.4cm). They can, however, also be built in multiples of this standard, that is, double-width, triple-width etc

NIM Logic Levels

  • LOGICAL 1 = -12 to 32 mA, or 600 mV to 1.6 V into 50 Ohm
  • LOGICAL 0 = < +2 mA or <100 mV into 50 Ohm


  • LOGICAL 1 = -14 to 32 mA, or 700 mV to 1.6 V into 50 Ohm
  • LOGICAL 0 = < +2 mA or <100 mV into 50 Ohm

Non-updating Discriminator
A discriminator whose output must return to a zero, or “off”, state before retriggering can occur.

A complementary output OR circuit

A logic circuit having the property that if at least one input is TRUE the output is TRUE

Overflow Suppression
A digital technique which allows to skip from the memory “out of range” values

In VME V430 compliant boards, a 3 row, 30 pin connector (plug) that mates with the JAUX connector

Peak Sensing ADC
An analog to digital converter which measures the peak amplitude of waveforms occurring within the GATE period

The ADC value readout when no input signal is present

The overlapping of amplifier output signals due to excessive count rate

Pole Zero Cancellation
A circuit that eliminates the undershoot of semi-gaussian shaped output pulses

Power Supply Rejection
The ability of a device to reject the effects of power supply variations

Programmable Logic Unit
A module which accepts a number of inputs and generates a logic combination of the inputs according to programmed operations

Charge ADC

Reflection Coefficient
The amount of signal amplitude that is reflected by an input due to impedance mismatch

Rise Time
The time required for a pulse to grow from 10% to 90% of full amplitude

It is the square root of < (X-< X >)2 > where X is a random variable and < > denotes the average

Sample and Hold
A circuit that on command samples and holds the instantaneous amplitude of an input signal

Sampling ADC
A device which samples an input waveform at specified time intervals, digitizes the analog values at the sampled points and stores the results in a digital memory


Semi-gaussian shaping
The pulse shape which resembles to a Gaussian curve obtained by CR-(RC)n filters with equal time constants

Shaping amplifier
An amplifier that accepts the output pulses from a charge-sensitive pre-amplifier and shapes them in order to improve the S/N ratio and minimise the risk of pile-up (tipically in energy spectroscopy applications)

Shaping time
The time constant of a shaping amplifier filter

Single Ended Signal
Ground referenced signal

Sliding Scale Technique
A technique employed to reduce ADC differential non linearity

Time to Amplitude Converter

Time-to-Digital Converter

A device which changes logical signals from one standard to another (e.g. from TTL to ECL)

Logical 0: 0 to 0.8 V;
Logical 1: 2.0 to 5.0 V

Updating Discriminator
A discriminator that can be retriggered before the output returns to zero

It is a VMEbus compatible crate type; in addition to the standard 3 row , 96 pin J1/J2 VME connectors, the V430 backplane adopts an extra JAUX connector providing ?2 V, -5 V (useful to supply ECL electronics without the need of on-board DC-DC converters) and ±15 V power lines, geographical address lines (SN1?5) and some User defined lines (CK, SG, CL)


Versa Module Eurocard; Master/Slave modular asynchronous computer architecture, used for data transfer, storage and processing (defined by IEEE-1014-1987 specifications); three card heights are allowed with VME; 3U, 6U, or 9U (1U = 43.60mm); a single slot card is 6T wide (1T = 5.08mm ). Length is either 160mm or 340mm.

An extension of the original VME specifications as defined by ANSI/VITA 1-1994; it offers, among the other features, larger 64-bit data path and 64-bit addressing range

A further extension of VME64 standard, providing, among the other features, geographical addressing capability and larger bandwidths for data transfer

VME64x extension for Physics: it features characteristics, stated as options in VME64x, helpful for the typical requirements of physics experiments, such as further user defined I/O pins and sparse data readout capability

Voltage Standing Wave Ratio: VSWR=Ei+Er/Ei-Er, where Ei is the incident wave amplitude and Er the reflected one

Zero Suppression
A digital technique that allows to skip from the memory the values that lie below a programmable threshold