Analog & Time to Digital Converter Glossary



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amplitude converter, data analyzer, digitizer, transient recorder, analog-to-digital converter, Msps, Gsps, GByte/s

Analog-to-digital Converters are integrated circuits that quantize a voltage or current into a stream of digital data. Board level products that make ADCs with sample rates of hundreds of Mega samples per Seconds (Msps) or several Giga samples per seconds (Gsps) accessible to the software are often called "digitizers" or "transient recorders". Unlike other ADC boards, our digitizers are optimized to detect pulses on the fly and stream the extracted sample data directly to the main memory, minimizing latency and CPU load. This is enabled by our custom 6GByte/s PCIe DMA controller that manages the buffer data structures directly without software intervention.

You also might like to have a look at the cronologic ADCs Ndigo5G-10 and Ndigo6G-12.


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An averager is an ADC digitizer that does not present single acquired waveforms to the user but does calculate the average of multiple waveforms before readout. This greatly reduces the amount of data that needs to be read out. It also takes away flexibility and makes it impossible to do processing on the individual pulses to improve the measurement results. Our Ndigo6G implements zero suppression together with very high readout bandwidth to enable software-based averaging without losing the ability to operate on individual pulses. Contact us to talk about the option of performing hardware averaging in the Ndigo6G.


bin size

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bin size jitter, FWHM, RMS, quantization error

In time-to-digital converters, the bin size is the unit of quantization for time measurements. In our TDCs other jitter sources are smaller than the quantization error. Therefore the measurement error for short intervals is dominated by the bin size in our devices. Under these circumstances, the maximum measurement error is close to half a bin. The rooted mean square (RMS) error is about 0.8 bins and the full width half maximum error is about 2 bins.



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cold target recoil-ion momentum spectroscopy, corresponding experimental setups are often called reaction microscopes, as well

Cold target recoil-ion momentum spectroscopy is a momentum imaging technique used to measure the complete fragmentation of an atomic or molecular few-body system. All charged fragments from an atomic, molecular, or surface reaction are projected onto large area position- and time-sensitive detectors. By measuring the individual particles’ times-of-flight and positions of impact on the detector, their 3D- momentum vectors are deduced. COLTRIMS measurements are coincidence measurements as many final-state fragments of single molecules or atoms are detected. Typical setups include a supersonic gas jet (i.e. molecular beam) as a target for the investigations and multi-hit capable MCP detectors with delay line position-readout for single particle detection.


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triggered measurements, common-stop

In a common-start setup, time intervals are measured relative to a trigger signal on the "start"-input that is arriving before the pulses shall be measured. In such a scenario, the gate signal specifies the start time of the time measurement while the individual channel inputs end the time period.


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triggered measurements, common-start

In a common-stop setup, time intervals are measured relative to a trigger signal that is arriving after the pulses that shall be measured. In such a configuration, the individual channel inputs deliver the start signal and the gate signal stops the measurement.

constant fraction discriminator

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When measuring the arrival time of pulses with a fixed threshold the time measured exhibits a measurement error that is a function of the pulse amplitude. For setups where pulses have varying amplitudes but a constant rise time, a constant fraction discriminator (CFD) can reduce this error. Measuring a signal at two or three fixed thresholds with a high-resolution TDC can achieve the same quality of time walk correction as a CFD.

cycle to cycle jitter

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short-term jitter, C2C jitter

Cycle-to-cycle jitter is a measure for the uncertainty in the interval between any two adjacent clock periods. In many TDC products, this is a major source of measurement error. For cronologic products, the cycle-to-cycle jitter is much less than the bin size. Care must be taken when comparing jitter specifications as various characteristics of the clock cycle distribution can be specified. Common specifications are the one sigma interval or the 95% interval of the distribution.



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Discriminators are circuits that are used to create a digital signal for time measurement from an analog input waveform. The simplest form is a threshold discriminator that compares the input with a fixed voltage. Commonly used are constant fraction discriminators that compare against a voltage proportional to the pulse height. 


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data acquisition

DAQ is the abbreviation for data acquisition. This is the process of sampling signals that measure real-world (analog) physical conditions and making them available to application software. In personal computers, this is accomplished by data acquisition cards such as cronologic ADCs and TDCs.

dead time

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Dead time describes a time interval during which a measurement device is not capable to acquire new measurements because it is still busy processing the previous one. Our products are optimized to minimize dead time. Read out always happens in parallel to measurement without disturbing it.


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Digitizer is a common name for board-level analog-to-digital converter products with high sample rates such as our Ndigo series of products, such as Ndigo5G-10 and Ndigo6G-12.

delay-line detector

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A delay-line position readout is used to measure the position of impact of a particle on a (typically larger area) MCP detector with a resolution of approx. 100µm. The electron cloud, which is emitted at the location of the particle impacted on the detector on the back of an MCP-stack induces a signal in a wire. The signal travels along the wire towards the wire’s two ends. By measuring the arrival time difference of the induced signal at each end of the wire, the position of impact on the wire can be deduced. In order to cover a larger area, the detection wire (i.e. the delay-line) is wound around a detector body. 2D-position of impact information can be obtained by employing a set of two orthogonal windings.

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fluorescence lifetime imaging microscopy

Fluorescence Lifetime Imaging Microscopy (FLIM) is a microscopy imaging technique where time-correlated single-photon counting (TCSPC) is performed on each pixel of the image. The sample is scanned by a high-frequency pulsed laser beam, single photons of the emitted fluorescence light are detected, and the arrival time of each photon in the laser pulse period is determined by the TCSPC system and recorded in a histogram.


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Functional Near-Infrared Spectroscopy

Functional Near-Infrared Spectroscopy (fNIRS) is a non-invasive method for brain imaging. In time-domain (TD) fNIRS the time-of-flight distribution (DTOF) of scattered photons is detected by multichannel time-to-digital converters

frequency counting

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frequency acquisition

In measuring the frequency of a periodic electronic signal, the number of cycles of oscillation, or pulses per second are counted. When it comes to recovering the frequency of the data pattern in a very short time or only in a few cycles, fast TDCs can improve the traditional method.


gate inputs

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In order to decrease the amount of data transmitted to the PC, some of our products include independent gating units that allow suppressing measurements during a time interval relative to the main trigger or a separate input signal.

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jitter counter

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A jitter counter is an instrument to measure timing jitter in clocks generators or communication systems. All cronologic TDC products can be used as jitter counters.

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LiDAR, and LADAR, "light detection and ranging", "laser imaging, detection, and ranging", "3-D laser scanning, Lidar mapping"

Light Detection And Ranging is a method where the round-trip time of a laser reflection is measured using a time-to-digital converter (TDC). It is used 3-D laser scanning both airborne and stationary, for computer vision especially in autonomous vehicles and meteorological measurements. 

low count rate detection

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particle detection, radiation detection, neutron detection, Geiger–Müller counter, scintillation counter, scintillation tracker, scintillation detector

Using single ion counting, low levels of radiation can be detected and characterized. In the area of radiation safety and non-proliferation small amounts of unknown nuclear material can be detected and identified using its spectra signature. Examples are special nuclear material (SNM) and shielded highly enriched uranium (HEU). 



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Matrix-assisted laser desorption/ionization

Matrix-Assisted Laser Desorption and Ionization is an ionization technique that can be used on large molecules with minimal fragmentation. This technology allows building time-of-flight (TOF) mass spectrometers for these molecules.

MCP detector

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microchannel plate detection, microchannel plate imaging, mcp imaging

A microchannel plate is an array of numerous electron multipliers consisting of parallel amplification channels distributed over a plane. It is used for the low-noise amplification of small currents of free electrons, ions, or high-energy photons and provides spatial information. During the measurement, the analyzed particles hit the plate and generate secondary electrons, which can then be detected with the help of fast TDCs or ADCs. MCP configurations with double or Z-stack MCP detectors are available for better resolution.

multi-channel scaler

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multi-channel detector scaler, MCS, multi-hit TDC, multi-hit converter

A multi-channel scaler (MCS) is a pulse counting instrument that records the number of events that occur during a specified time interval and provides a time-histogram of counts versus time. MCS are commonly used in single-photon counting applications. All cronologic time measurement products can be used as multi-channel scalers.



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Nuclear Instrumentation Module standard

The NIM standard, originally an acronym for Nuclear Instrumentation Module, was developed in nuclear and high-energy physics in 1964. The included standards define mechanical and electrical specifications for modular systems with bus connections.


Optical Coherence Tomography

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Optical coherence tomography is a high-resolution imaging system. It obtains 2- and 3-dimensional images from scattering materials (e.g. biological tissue). As a non-invasive diagnostic instrument, it is mostly used for ophthalmological examination of the retina. In this application, analog signals are sampled with ADCs so that the resulting digital pattern represents the analog signal as a function of the change in wavelength of the light source.


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optical time-domain reflectometry

In optical fiber communications, the losses in optical fibers can be measured with optical time domain reflectometers. The measuring method works similar to radar but works with very low light levels and helps to localize poor fiber splices or faulty optical components. For measurement, a fast rise time pulse is injected into the cable system at one end. If the traveling impulses arrive at a location where the impedance differs from the characteristic impedance of the cable (e.g. at a faulty link), some of these signals will be reflected back to the source and can be detected with photon-counting detectors, photomultipliers, or avalanche photodiodes. With help of a fast ADC, the time parameters of the reflection are measured in order to determine the location of the impedance discontinuity.


PALM microscopy

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photoactivated localization microscopy, PALM imaging, Single-molecule imaging, Single-molecule localization microscopy, SMLM, single-molecule microscopy

Photoactivated Localization Microscopy (PALM) is a super-resolution imaging technique that achieves nanometre-scale resolution by exploiting the properties of photoactivatable fluorophores to reveal spatial details of tightly packed molecules. This method enables the detection of individual molecules such as proteins in a cellular context. The method offers a high level of detail when depicting 3D structures in cell bodies and works like this: 

Exposing fluorophores to low-power activating lasers of a certain wavelength leads to a change in their emission spectra. This conversion is implemented stochastically so that only a few fluorophores will turn into their active state. The stochastic excitation of the fluorophore ensures that each fluorescence point comes from a single fluorophore. A high-power laser beam briefly exposes these activated molecules, after which they are immediately returned to their inactive state (e.g. by photobleaching). This process is then repeated over thousands of images and the frames are merged into a super-resolution image.

photon counting

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single-photon detectors, SPD, detection of individual photons, photosensors, multi-pixel photon counter

In single-photon counting, a single-photon detector (SPD) emits an electric pulse every time a photon is detected so that individual photons can be counted. Photon counting is used in telecommunication, biophysics imaging (e.g. FLIM), quantum optics and high-resolution (single-pixel) LIDAR, OTDR (optical time-domain reflectometry) and Quantum Key Distribution (QKD).


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PCI eXtensions for Instrumentation

PCI eXtensions for Instrumentation is a bus system for measurement and automation technology. It is based on the older xPCI bus technology but uses the point-to-point PCI express standard for communication. Our standard PCIe products allow customers to build systems that deliver the same performance as a PXI setup at a fraction of the cost.


Quantum key distribution

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The quantum key distribution enables tap-proof encryption of data. For this purpose, the quantum properties of light are used to transmit encrypted data. Single-photon sources (SPS) are used for optimal performance. Our fast TDCs can be used in single-photon counting receiver modules that convert single-photon detection events into streams of timestamps.


reciprocal counter

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A reciprocal counter measures a frequency by measuring the time between a certain number of edges of a clock signal. This is opposed to the approach of a simple counter that counts the number of signal edges in a certain time interval. All of our TDCs can be used as reciprocal counters with very high precision. To measure frequencies that are higher than the maximum count rate of a given TDC an external prescaler is required.

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Time Correlated Single Photon Counting, time domain FLIM, tdFLIM

In Time-correlated single-photon counting (TCSPC) fluorescence decays are measured over the time axis. The method is an essential part of fluorescence lifetime imaging microscopy (FLIM). Time-Correlated Single Photon Counting is considered a particularly gentle measurement technique because the light pulses required for sample excitation have low pulse energy. This is possible because only a single photon is processed at a time. TCSPC is based on the detection of these individual photons and the measurement of their arrival times in relation to a reference signal, which is usually the time of emission of the laser pulse that was used to excite the sample. This laser pulse occurs with a high repetition rate so that a sufficiently high number of individual photons can be determined for the resulting measurement of the fluorescence lifetime.


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Timing Generator

Most of our ADC and TDC products are equipped with this feature which is a great help to control your experimental setup. The TiGer can be used to output periodic Timing patterns, delayed copies of other signals, or random triggers among other use cases.

trigger matrix

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trigger blocks, mapping

In most cronologic products, any digital input can be used to trigger any triggerable circuit. The mapping is performed by the configurable trigger matrix. Inputs can be input connectors, TiGer pattern generators, software triggers, and others. Triggerable circuits can be input gates, TiGer pattern generators, auxiliary ADC measurements among others. 

transient recorder

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Transient recorders are oscilloscopes that are designed to measure waveforms with very high bandwidth. Unlike equivalent time sampling scopes a transient recorder acquires the measurement in a single shot. The signal does not need to be repetitive. For digital data acquisition products, the terms ADC, digitizer, and transient recorder are mostly used interchangeably. 


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TOF- & MASS- spectroscopy / spectrometry detectors, TOFMS, ion-counting, ionization spectroscopy

In time-of-flight mass spectrometers ions are accelerated in an electric field. The time it takes for the ion to reach a detector is used to determine the mass-to-charge ratio of the ion. With a constant-fraction-discriminator (CFD) and time-to-digital converters, the flight time of the ion can be easily be measured with high precision. In setups where a high number of ions of the same mass is created, an ADC digitizer can be used instead to also obtain information on the pulse height and thus on the number of ions in each measured pulse.

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zero suppression

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All of our ADCs feature onboard zero suppression. The idea of this feature is, that only data that meet specifications predefined by the user are transmitted. This reduces PCIe busload in order to make maximum use of the available readout bandwidth. When set up correctly, only relevant pulses (above a certain threshold level) are detected, so that the amount of data that needs to be copied and analyzed is reduced drastically.