LTR25 Sigma-delta ADC for vibrometry, phasemetry, acoustics, seismometry

Sigma-delta ADC for vibrometry, phasemetry, acoustics, seismometry
  • Eight synchronous channels, 24 bits
  • Sampling rate up to 78 kHz per channel
  • Direct connection of up to 8 ICP sensors without any additional devices
  • Built-in power supply sources ICP-sensors 2,86/10 mA in each channel
  • Phase frequency response is close to linear
  • Anti-aliasing filters
  • Monitoring the short-circuits or break in the circuits of ICP sensors during the measurement

Specialized module for connecting ICP sensors to 8 channels.

LTR25 is intended for application in tasks requiring high quality digitization of an alternating signal with high spectral fidelity conversion, with a wide dynamic range and a large signal-to-noise ratio. The module allows to detect short-circuits and break of ICP-sensors lines directly during the measurement.  The 8 channels of the 24-bit LTR25 ADC are strictly parallel, independent, without switching delay between themselves.

Specialized 8-channel ADC LTR25, as compared with a universal 4-channel ADC LTR24-2, has a lower cost of a measurement channel while constructing systems with ICP sensors.

The main sphere of application of LTR25: vibration monitoring, vibrodiagnostics, phasemetry, acoustics, seismometry, audio processing.

LTR25 is also compatible with IEPE sensors from CCLD, Isotron®, Deltatron®, Piezotron® . Also LTR25 is compatible with 2-wire TEDS-sensors with built-in preamplifiers, according to the IEEE 1451.4 (Class 1 MMI), with support for only analog mode.

Number of channels 8 channels of ICP sensors connection
Resolution of sigma-delta ADC 20/24 bits depending on the settings
Maximum conversion frequency (Fпр) of the ADC 78 kHz
Minimum conversion frequency of the ADC 610 Hz
Synchronization of ADC channels All 8 channels of the LTR25 module are strictly synchronous, the relative phase shift is minimal.
Phase shift with multimodule input Within the same LTR, the relative phase shift of the data acquisition between the LTR25 modules will always remain constant in time.
Possible combinations of the ADC conversion frequency, the ADC output format and the number of channels

Frequency of ADC data acquisition, kHz

(is equal to Fпр)

The supported combination of the ADC data format and the number of channels
ADC data format
20 bits 24 bits
Number of channels
78,1 1÷6 1÷3
39,1 1÷8 1÷6
19,5; 9,77; 4,88; 2,44; 1,22;  0,610 1÷8
The full operating range of the signal voltage relative to AGND From 0 to +22 V
Voltage measurement range "~ 5 V" (rms value of the variable signal component when the amplitude of the variable signal component is not exceeded "± 10 V")
The value of direct current in the ICP-sensor circuit at a voltage of 0 to 22 V 10 mA ± 2% (10 mA range)
2.86 mA ± 2% (2.86 mA range)
The signal/(noise + harmonic) ratio over the sinusoidal signal (SINAD), a typical value 92 dB
Input resistance of LTR25 ICP circuit at a voltage of 0 to 22 V in operating mode

- With constant current: not less than 5 MOhm (to be specified)

- With alternating current in the transmission bandwidth: not less than 30 kOhm (impedance module)

Limits of the permissible basic reduced (to the final value of the subband) error in measuring the rms AC voltage, under the following conditions:

± 0.1% (for the frequency range from 25 Hz to 0,43 Fпр)
Lower limit of frequency response 1.3 Hz at the -3 dB level
Upper limit of frequency response 0.49 of the set conversion frequency at -3 dB
Inter-channel interference Less than -100 dB
Galvanic isolation
See the main features of LTR modules

DSP functions currently implemented in FPGA

(see the note below)


1. Filtration: 2 links of FIR filter (up to 33rd order of each link) with downloadable 32-bit filter coefficients
2. Decimation of data from 1:2 to 1:64
3. Correction of data "on the fly" in accordance with the calibration coefficients
4. Insertion into the data stream: the signs of short circuit or a break of sensor for each channel

Note: A large unused computational resource in FPGA Cyclone IV (more than 75%) allows in the future to implement vibration speed calculation, to develop filtering capabilities and to implement other DSP algorithms within LTR25 with both fixed and floating arithmetic. Multipurpose 2 MB flash memory is used for FPGA firmware storage and calibration coefficients, more than 1 MB is free for further development. FPGA is automatically downloaded from Flash memory. FPGA firmware is remotely updated.

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


Signal connector of LTR25


  • ltr25api_en.pdf (filesize: 437 853 bytes, date: 15.02.2018)

    LTR25 module. 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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