LTR22 Sigma-delta ADC for vibroacoustic measurements

Sigma-delta ADC for vibroacoustic measurements
  • Parallel ADC channels and synchronization signals SYN_IN and SYN_OUT allow to create multi-channel (multi-module) synchronous data acquisition systems
  • ±15V supply voltage output to the external connector of the module provides convenient connection of intermediate active low-power devices (for example, LE-41 charge amplifier) or active sensors

LTR22 is intended for registration of dynamic vibroacoustic signals with the possibility of further program spectral analysis.

Four parallel channels, each of which has: high-quality differential input, sigma-delta ADC, anti-aliasing filter; and a software-enabled high-pass filter with a cutoff frequency 0.7 Hz, to compensate for the DC component of the signal.

All four channels are synchronous, which makes it possible to apply this module to the tasks of signal phasometry, for example, in hydroacoustics and low-frequency paths of location.

A more advanced alternative to LTR22 is the LTR24-1 module, compatible on the connector's pins.

Number of channels 4 with differential input
Resolution 16 bits
Input signal measuring subranges ±10 V, ±3 V, ±1 V, 
±300 mV, ±100 mV, ±30 mV
Conversion frequency from 3.472 kHz to 78.125 kHz 
(given by formula and fixed frequency grid)
Input resistance of differential input, not less than 10 MOhm when on
1 kOhm when off
Maximum permissible voltages at analog inputs (input protection) ±20 V when ON
±20 V when OFF
Limits of the allowed basic reduced error of measuring the DC voltage at the conversion frequencies of the ADC 78.125 kHz; 39.062 kHz; 17.361 kHz ±1.0% at the measurement sub-range ±30 mV
±0.5% at the measurement sub-range ±100 mV
±0.2% at the measurement subbands ±300 mV, ±1 V, ±3 V, ±10 V
Limits of the allowed basic reduced (to the final value of the subband) error of measuring the voltage of the rms AC value (without the normalization of the amplitude-frequency characteristic) at the conversion frequency of the ADC 78,125 kHz:
– At an input signal frequency of 0.02 ... 5 kHz
±0,15 % For measurement subbands
±10 V, ±3 V, ±1 V
±0,3 % For measurement subbands
±300 mV, ±100 mV, ±30 mV
– At an input signal frequency of 5 ... 15 kHz
±0,5% For measurement subbands 
±10 V, ±3 V, ±1 V
±1% For measurement subbands 
±300 mV, ±100 mV, ±30 mV
– At an input signal frequency of 15 ... 25 kHz
±2 % For measurement subbands
±10 V, ±3 V, ±1 V
±4 % For measurement subbands
±300 mV, ±100 mV, ±30 mV
Common mode 50 Hz rejection ratio at differential mode Not less than 80 dB
Inter-channel interference of a sinusoidal 1 kHz signal at all subbands Not more than -80 dB
Sync modes Internal, external synchronization of data acquisition start, multi-module synchronization of several LTR22
Synchronization input SYN_IN Compatible with the output logic level of TTL/CMOS-elements with supply voltage of +3.3 V / +5 V; The input has a resistor pull-up of 20 kOhm to the AGND circuit.
Synchronization output SYN_OUT It has an output logic level of CMOS/LVTTL elements with supply voltage of +3.3 V, by default it is in the Z-state with a resistor pull-up of 20 kOhm to the AGND circuit. The output is used for multi-module synchronization of LTR22.
External power supply outputs
Output voltage ±15 V
Maximum load current 50 mA per each output relative to the AGND circuit
Output impedance 26 Ohms per each output
Galvanic isolation
See the main features of LTR modules

 External signals connector

Hardware description, assignment and connection of signals is given in the User's Guide.


  • ltr22api.pdf (filesize: 1 001 935 bytes, date: 26.04.2007)

    LTR212 module. Ltr212api library. Programmer's Guide.

  • ltrapi_en.pdf (filesize: 604 618 bytes, date: 15.02.2018)

    Ltrapi basic library. Programmer's Guide.

  • ltr_cross_sdk_en.pdf (filesize: 551 553 bytes, date: 13.02.2018)

    Description of the software for Windows, Linux, FreeBSD and QNX.

  • ltr_en.pdf (filesize: 11 066 427 bytes, date: 25.12.2017)

    LTR modular DAQ system. User's Guide (revision 3.1.0).

    • General characteristics and principles of construction
    • Working with LTR crate
    • Overview of LTR crate architecture
    • LTR11 ADC module
    • LTR212 (M) strain measurements modules
    • LTR27 measuring module
    • LTR41, LTR42, LTR43 digital I/O and synchronization modules
    • LTR51 frequency meter module
    • LTR22 ADC module
    • LTR24 (-1, -2) ADC modules
    • LTR25 ADC module
    • LTR34 DAC module
    • LTR35 DAC module
    • LTR114 ADC module
    • LTR210 ADC module
    • LTR00 Dummy module
    • Low-level programming of LTR-EU crate
    • Specification
  • ltr_soft_getting_started_en.pdf (filesize: 269 974 bytes, date: 13.02.2018)

    Starting to work with DAQ system LTR. Questions about the software.

LGraph2 software package

  • (filesize: 26 786 707 bytes, date: 11.10.2021)

    LGraph2 is a free multi-channel data recorder for Windows. Version 2.35.20 provides the possibility of simultaneous data visualization and recording from the ADCs: L-502, L-780M, L-783, L-791, E-502, E14-140, E14-140M, E14-440, E-154, E20-10, LTR11, LTR114, LTR27, LTR212, LTR216, LTR22, LTR24, LTR25, LTR51. It requires an updated version of the LComp driver (from version 01.04.2010) and ltrserver (no lower than

Software for Windows

  • lcard-opc-setup.exe (filesize: 12 440 520 bytes, date: 09.04.2019)

    OPC DA Server for L Card data acquisition modules and LTR crate system. Version 1.0.10.

  • lcomp.exe (filesize: 6 342 216 bytes, date: 12.05.2021)

    Beta version. LCOMP library for Windows XP/Vista/Win7/Win8/Win10 32 and 64-bit versions with drivers. The installer and drivers are digitally signed. The library is built on the basis of modern WDM-drivers rewritten on WDF. It includes the WDM driver itself for L-CARD hardware, the DLL library with source code, programming examples, electronic description, etc. The LCOMP library provides support for almost the entire range of products: PCI boards, USB modules. ISA support is excluded.

    The library includes “L-Graph I” software. L-Graph I supports the following devices: L-1450, L-761, L-780, L-783, L-791, E14-140, E-154 and E14-440. Files recorded by L-Graph I can also be read and processed using the demo-version of PowerGraph v.3.X.

  • ltrd-setup.exe (filesize: 1 467 408 bytes, date: 19.08.2021)

    The ltrd service. Version Provides communication with LTR crates. It is a replacement for the LTRserver software while maintaining the compatibility of the program interface. ltrd is designed for the same purpose as LTRserver, but it is a service that runs when the system is started. The graphical interface to the service is provided by a separate LTR Manager program.

    Attention! Only one of the programs ltrd or LTRserver can work at a time.

  • ltrdll.exe (filesize: 1 328 600 bytes, date: 30.11.2021)

    Libraries for working with LTR crates and modules. Version 1.32.30.

  • ltrmanager_setup.exe (filesize: 9 751 808 bytes, date: 04.05.2021)

    LTR Manager software. Version 1.5.2. Graphical interface to the ltrd service. Provides an interface similar to the LTRserver interface when working through the ltrd service.


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