LTR24 Sigma-delta ADC for vibrometry, phasemetry, acoustics, seismometry

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

Four synchronous channels, 24 bits
Sampling rate up to 117 kHz per channel
Additional 4 inputs for connecting ICP sensors or strain gauges (for LTR24-2)
High DC accuracy
Phase-frequency characteristic is close to linear
Anti-aliasing filters
DC compensation mode
Monitoring mode of short circuit or break in the ICP sensor circuit (for LTR24-2)
Reservation

LTR24 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. LTR24 also has high accuracy in the measurement of direct current.

The main applications of LTR24 are: vibration monitoring, vibration diagnosis, phasometry, acoustics, seismometry, audio processing, general-purpose laboratory ADC for the study of physical processes.

LTR24-1 modification can be considered a universal ADC due to the presence of a high-quality differential input ±10V, high resolution, normalized characteristics of measuring accuracy of the DC and AC voltage.
LTR24-2 modification, in addition to the differential inputs, has the ability to directly connect to the ICP sensor inputs (with a test mode for detecting short circuits and breaking lines of ICP sensors).

Each input of ADC module's four channels can be independently programmed to permanently connect to the differential input or to the input of the ICP-sensor. Four ADC channels are strictly parallel, independent, without switching delay between themselves. Spectrally pure conversion with effective anti-aliasing filters. The output of ±15 V to 30 mA provides direct connection of low-power preamplifiers (for example, LE-41). LTR24-2, due to the presence of 4 sources of stable current 2.86/10 mA), also has the additional possibility of connecting single strain gages with a 4-wire circuit for vibration measurement tasks in the audio frequency band (indirect measurement of the AC voltage at a known current through a strain gauge).

LTR24-2 on the ICP input is also compatible with the CCLD, Isotron®, Deltatron®, Piezotron® IEPE-sensors, and is also compatible with 2-wire TEDS-sensors with built-in preamplifiers according to the IEEE 1451.4 (Class 1 MMI), with support only analog mode.

Fast commutation
of external signals
There are several holes in the board to fix a cable assembly.

37-pin interface terminal block board

DB-37F-increaser

General characteristics (LTR24-1, LTR24-2)

Number of channels

4 channels, each channel is programmable either for the differential input mode (inputs X, Y), or for the ICP sensor connection mode (there are separate contacts on the module connector for connecting ICP sensors). Each channel has a high-quality differential high-impedance input with a high in-phase rejection ratio.

Resolution of the sigma-delta ADC

20/24 bits depending on the settings

Maximum ADC conversion frequency

117 kHz

Minimum ADC conversion frequency

610 Hz

The mode of measuring the intrinsic zero-point voltage

Programmed simultaneously for all channels

The AC mode "with DC compensation" or the normal mode "DC+AC"

Programmed separately for each channel

Residual zero offset of the inverter in "AC" mode

5 mV (at the sub-band of ±10 V)
1 mV (at the sub-band of ±2 V)

Linearity of the phase-frequency characteristic (PFC)

At the "AC+DC" mode, the PFC is linear in the entire frequency range. In the "AC" mode, the PFC is linear, with the exception of the low frequency region (less than 5 Hz), where the DC compensation mechanism has an active influence on the AFC.

Synchronization of ADC channels

All 4 channels of the LTR24 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 LTR24 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	Supported combination of ADC data format and the number of channels
	ADC data format
	20 bits	24 bits
	Number of channels
117,1	1÷4	1÷2
78,1	1÷4	1÷3
58,5 and lower	1÷4

Note: The limitations for the LTR-U-1-4 crate can be found in the User's Guide.

Power consumption (with unloaded outputs +15 V, -15 V)

3.0 W (LTR24-1)
3.5 W (LTR24-2, ICP inputs arenot connected)
3.5 W (LTR24-2, ICP inputs are connected, current is 3 mA)
4.6 W (LTR24-2, ICP inputs are connected, current is 10 mA)

External power supply outputs

Output voltage

±15 V

Nominal output current

30 mA for each output relative to AGND circuit
10 mA (for LTR24-2 with ICP inputs enabled)

Output impedance

22 Ohms per output

Characteristics when working with differential inputs (LTR24-1, LTR24-2)

Input signal measuring subranges

±10 V, ±2 V (peak values)

Common-mode voltage of the differential input

±10 V (independent of subband)

Operating range of signal relative to AGND

±12 V (at inputs X, Y)

Operating range of DC component compensation in AC mode

at the sub-band of ±10 V:

±1,7 V;
±10 V (if variable component is within ±1 V)

at the sub-band of ±2 V:

±2,5 V;
±4,5 V (if the variable component is within ±0.25 V)

Limits of the permissible basic relative error in measuring the DC voltage of positive and negative polarity in the "Differential input" mode, in percent

where X_К is the final value of the established measurement subband (X_К = 10 V or 2 V);

X – a value by LTR24, V.

Limits of the permissible basic relative error in the measurement of the rms AC voltage in the "Differential input" mode, in percent

ADC frequency, kHz (Fпр)	Signal frequency at “DC+AC” mode	Signal frequency at “АС” mode
610,352; 915,527; 1220,7; 1831,05; 2441,41; 3662,11; 4882,81; 7324,22; 9765,63; 14648	From 1 Hz to 0,43Fпр	From 25 Hz to 0,43Fпр
19531; 29297; 39063	From 1 Hz to 0,25Fпр	From 25 Hz to 0,25Fпр
19531; 29297; 39063	From 0,25Fпр to 0,43Fпр	From 0,25Fпр to 0,43Fпр
58594; 78125; 117188	From 1 Hz to 0,25Fпр	From 25 Hz to 0,25Fпр
58594; 78125; 117188	From 0,25Fпр to 0,43Fпр	From 0,25Fпр to 0,43Fпр

Notation: X_К1 – the final value of the established measurement subband (X_К = 10 V or 2 V); X – a value by LTR24, V.

In-phase 50 Hz rejection coefficient in differential mode, not less than

77 dB

Common mode 50 Hz rejection coefficient in differential mode, not less than

75 dB

Input resistance of differential input (along any line X1...X4, Y1...Y4 relatively to the AGND circuit) when the module state is ON

Not less than 10 MOhm

Input current along the lines X1...X4, Y1...Y4 at a voltage of ±10 V

±0.2 nA (under normal conditions)
±3.0 nA (in the operating temperature range)

Maximum allowable voltage

±20 V (at the inputs X1...X4, Y1...Y4)

AFC lower limit

0 Hz (at DC+AC mode)
0,48 ±0,60 Hz, by level of –3 dB (at AC mode)

AFC upper limit

0.49 of the set conversion frequency by the level of -3 dB

Signal-to-noise ratio, typical value

102 dB

The signal/(noise + harmonic) ratio over the sinusoidal signal (SINAD), typical value

97 dB

The coefficient of nonlinear distortion (THD), typical value

100 dB

Dynamic range, free from spurious emissions (SFDR), typical value

101 dB

Inter-channel interference at a frequency of 5 kHz

Less than -90 dB

Own noise, typical value, with shorted input

– With a conversion frequency of 117.188 kHz
9 μV	2 V range
42 μV	10 V range
– With a conversion frequency of 39.063 kHz
6 μV	2 V range
26 μV	10 V range
– With a conversion frequency of 9.766 kHz
4,5 μV	2 V range
23 μV	10 V range

Reservation

Supports the possibility of a redundant connection (only via differential input) more than one LTR24 to the same signal sources.

Amplitude spectrum. It is received when a sinusoidal signal of 1.3 kHz is applied to LTR24 differential inputs for the 2 V range.
The "0 dB" level at the spectrum corresponds to the maximum amplitude of the signal in the set subband. It uses an FFT of 20,000 points with a Blackman-Harris window.

Amplitude spectrum. It is received when a sinusoidal signal of 1.3 kHz is applied to LTR24 differential inputs for the 10 V range.
The "0 dB" level at the spectrum corresponds to the maximum amplitude of the signal in the set subband. It uses an FFT of 20,000 points with a Blackman-Harris window.

Characteristics when working with ICP-inputs (LTR24-2)

Operating range of signal relative to AGND

From 0 to 22 V (at the ICP inputs)

Operating range of DC component compensation in AC mode

From 0 to 22 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)

Instability of the current source relative to the calibrated current value

± 0.05% of the calibrated value (under normal conditions)
± 0.15% of the calibrated value (full temperature range)

Internal resistance of ICP circuits at a voltage of 0 to 22 V in operating mode

At least 2.7 MOhm (at DC)
At least 25 kOhm (at AC in the frequency pass band)

Limits of the permissible basic relative error in the measurement of the rms AC voltage in the "ICP input" mode, in percent

ADC frequency, kHz (Fпр)	Signal frequency	%
610,352; 915,527; 1220,7; 1831,05; 2441,41; 3662,11; 4882,81; 7324,22; 9765,63; 14648	From 100 Hz to 0,43F_пр
19531; 29297; 39063	From 100 Hz to 0,25F_пр
19531; 29297; 39063	From 0,25F_пр to 0,43F_пр
58594; 78125; 117188	From 100 Hz to 0,25F_пр
58594; 78125; 117188	From 0,25F_пр to 0,43F_пр

Notation: X_К2 – the final value of the established measurement subband, X_К2 = 5 V or 1 V;

Maximum allowable voltage

-1…+27 V at a current of not more than ± 30 mA (at the ICP1-ICP4 inputs)

AFC lower limit

1.3 Hz at the -3 dB level

AFC upper limit

0.49 of the set conversion frequency at the -3 dB level

The mode of indirect resistance measurements (LTR24-2)

Resistance measurement ranges at the "DC + AC resistance" mode

0…1000 Ohm (at a current of 10 mA and a range of ±10 V)
0…3496 Ohm (at a current of 2,86 mA and a range of ±10 V)
0…200 Ohm (at a current of 10 mA and a range of ±2 V)
0…699 Ohm (at a current of 2,86 mA and a range of ±2 V)

Resistance measuring ranges at the mode of measurement of "AC resistance" signal variable component (in vibrometry tasks)

±R/2 at sensor resistance R = 0...1000 Ohm (at a current of 10 mA and a range of ±10 V)
±R/2 with a sensor resistance R = 0...3496 Ohm (at a current of 2.86 mA and a range of ±10 V)
±R/2 at sensor resistance R = 0...200 Ohm (at a current of 10 mA and a range of ±2 V)
±R/2 with a sensor resistance R = 0...699 Ohm (at a current of 2.86 mA and a range of ±2 V)

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.

LTR24-1

4 parallel channels, 24 bits, up to 117 kHz
LTR24-2

4 parallel channels, 24 bits, up to 117 kHz, direct connection of ICP sensors

LTR24-1

LTR24-2

Descriptions

ltr24api_en.pdf (filesize: 300 955 bytes, date: 15.02.2018)
LTR24 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

lgraph2.zip (filesize: 26 783 707 bytes, date: 19.03.2021)
LGraph2 is a free multi-channel data recorder for Windows. Version 2.35.16 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 1.5.2.1).

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: 6 342 096 bytes, date: 20.01.2021)
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: 1 467 072 bytes, date: 25.11.2020)
The ltrd service. Version 2.1.8.6. 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: 1 293 128 bytes, date: 12.01.2021)
Libraries for working with LTR crates and modules. Version 1.32.22.
ltrmanager_setup.exe (filesize: 7 981 824 bytes, date: 25.11.2020)
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.