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16-Channel Signal Conditioning System with Integral 24-bit Precision DAQ
On the New Frontiers of Precision
SDAS
Precision Signal Data Acquisition Systems
Introduction
The Precision SDAS16 is a 16-channel data acquisition system that combines Precision Filters proven signal conditioning front ends with the latest 24-bit A/D converter technology. Five SDAS16 configurations are available for voltage, dynamic strain, charge, bridge, and IEPE sensors to cover a wide range of measurements. 24-bit digitizers support synchronized sampling at up to 312.5 kilosamples per second (kSPS) per channel for 135 kHz analog signal bandwidth measurements. Unprecedented accuracy is assured via digital calibration from the sensor interface through A/D conversion. Multiple SDAS16 units may be distributed around the test article and tightly time-stamped and synchronized via IEEE-1588-2008 (IEEE-1588v2 PTP) protocol or IRIGB. Data streams over 1 GB Ethernet to the host(s) for analysis and storage.
The SDAS16-BRG variant provides bipolar constant voltage excitation to bridge type sensors and supports shunt calibration and automatic bridge balance. The BRG version is compatible with the latest Kulite 5th-wire equipped transducers for enhanced accuracy pressure measurements at high temperatures. Options for ¼-bridge 120, 350, 1000 or custom bridge completion are available.
The SDAS16-BCC variant for dynamic strain measurements features Precision’s Balanced Constant Current (BCCTM) technology. Precision Filters developed BCC to allow for wide dynamic range measurement of strain in harsh environments using only a two-wire connection to the gage. The circuit is insensitive to changes in lead resistance with temperature and since the circuit is balanced, the differential input amplifier rejects noise pickup in the leads. Additionally, the circuit will continue to measure strain even if a gage terminal shorts to the test article.
The SDAS16-CHG variant is compatible with all standard piezoelectric sensors for measuring pressure and vibration, and includes compensation circuitry to allow for low frequency operation with the highest temperature sensors where conventional charge amps fail. The amplifier features shunt calibration and innovative T-insertion for sensor and cable verification.
The SDAS16-IEPE supports piezoelectric sensors with integral electronics to convert the charge to voltage internal to the sensor. Programmable IEPE current accommodates a wide range of sensors and cable lengths. Floating and grounded sensor mounts are supported for single and multi-axis sensors meaning your measurements will be free from ground loop noise.
The SDAS16 variant without front end signal conditioning supports high-level voltage inputs and is the ideal solution for adding digitizers to Precision Filters 28000 Systems or for other applications where precision DAQ is desired for preconditioned signals.
Each SDAS system is equipped with buffered and conditioned analog outputs to support third party DAQ systems, control systems, safety systems or other applications.Built-in Go/No-Go routines that verify the setup prior to a test run are initiated via a Windows-based desktop client application. The desktop client also provides group setup for multiple SDAS16 systems along with time domain and frequency domain multi-scope display capability, allowing the user to monitor real time SDAS16 data. The SDAS16 is easily integrated into common third party applications such as LabView and APEX via the C callable API.
Key Features
Applications
Input Amplifier
Number of Channels: 16
Type:
Balanced differential input with programmable AC/DC coupling
Input Impedance:
10 MΩ//100 pF per side
Max Level (AC+DC+Common Mode):
± 10 Vpk for f ≤ 200 kHz, ± 10 Vpk x (200 kHz/f) for f > 200 kHz
Input Protection:
30 V continuous (power on), 60 Vpk transient (1 ms pulse, 50% duty cycle)
Spectral Noise (RTI):
11 nV/√Hz at 1 kHz and gain ≥ 100
Noise:
350 nVpk-pk RTI, 0.1 Hz to 10 Hz, gain ≥ 100
2.8 μVrms RTI + 60 μVrms RTO, 10 Hz to 100 kHz BW
AC Coupling Frequency (- 3 dB):
0.159 Hz
CMRR:
90 dB DC to 440 Hz, gain ≥ 10 (Filter/Amp Mode, DC Coupled)
Programmable Gain:
x1, x10, x100, x1000; x1 fixed gain for A/D only variant
DC Accuracy:
0.03% after auto-calibration, ±5 °C from Tcal
Drift:
1 μV/°C RTI + 60 μV/°C RTO
Low-Pass Filter:
Three-pole Butterworth (60 dB/decade): −0.1 dB at 200 kHz, -3.01 dB at 375 kHz
Conformance to Theoretical Filter Response:
± 0.1 dB to 100 kHz; ± 0.2 dB 100 kHz to 200 kHz
Crosstalk:
− 80 dB DC to 100 kHz
Input Test Modes:
RUN, TESTBUS, TESTBUS_X1, SHORT, AC_Current (BCC only), EXC_Off (BCC, BRG Only), Shunt_Cal (BRG only)
Mute Mode:
Terminate unused channels or channels with faulty sensors to a quiet state
Analog Output:
Buffered output available at front panel of chassis via 50-pin D connector
Specifications
16-Channel Voltage SDAS (A/D Only)
Inputs Provided on 50-pin D Connector
16-Channel Bridge (shown) and Dynamic Strain SDAS
Inputs Provided on 26-pin D-sub Connectors (x8)
16-Channel Charge (shown) and IEPE SDAS
Inputs Provided on BNC Connectors (x16)
Digitizer
Type:
24-bit simultaneous sampling converter, sigma-delta type
Programmable Sampling Rates (Fs):
2.5 kSPS to 312.5 kSPS per channel
Alias Rejection:
102.5 dB, typical
Time Stamping and Synchronization
Description
All ADCs in a single SDAS16 box are synchronized to provide simultaneous sampling across all 16 channels. Multiple SDAS16s connected to an IEEE-1588v2 PTP network will be synchronized to each other and the Grand Master clock to within 20 nsec (rms) channel-to-channel. In effect, all channels in a multi-box system will be synchronized and sample simultaneously. Time stamping on an IEEE-1588v2 PTP network is provided by hardware at the network MII interface and conforms to IEEE-1588-2008.
Multiple SDAS16 boxes connected to a network that does not support IEEE-1588 can be synchronized using one of two available methods:
1) Via 1PPS/INOUT daisy chained to all boxes, again with one Master (drives 1 PPS) and the rest Slaves (receive 1PPS). The Slave boxes lock onto the Master 1PPS signal to provide synchronous ADC sampling clocks for every box. There will be box-to-box skew depending on cable lengths, but all channels will be synchronized. The system, however, will be unaware of actual time and will have to rely on system time.
2) IRIGB Time Code Standard, DCLS (TTL) and AM modes are supported.
Description
FLAT and PULSE mode digital low-pass filters are selectable to match the requirements of a particular test. The FLAT mode is recommended for tests such as frequency domain analysis where flat passband and sharp roll off are required to maximize the signal bandwidth for a given sampling rate. For time domain measurements, transient testing or control loop applications, the PULSE mode is advised.
Flat Mode Characteristics
DC Gain: 0 dB
Passband Ripple: 32 μdB
Ripple Bandwidth (Hz): 0.4*Fs
−0.1 dB Bandwidth (Hz): 0.401*Fs
−3 dB Bandwidth (Hz): 0.433*Fs
Stopband Frequency (Hz): 0.499*Fs
Stopband Attenuation (Hz): 110 dB
Complete Settling Time (Sec): 79.6/Fs
Group Delay (Sec): 39.8/Fs
Specifications
Pulse Mode Characteristics
DC Gain: 0 dB
−0.1 dB Bandwidth (Hz): 0.0342*Fs
−3 dB Bandwidth (Hz): 0.1861*Fs
Stopband Frequency (Hz): 0.813*Fs
Stopband Attenuation (Hz): 79.4 dB
Complete Settling Time (Sec): 6.5/Fs
Group Delay (Sec): 3.25/Fs
Response Plots
Low-Pass Filter Modes
Sensor Type:
Any bridge-type sensor, static strain, dynamic strain, AC or DC voltage
Input Connector:
8 ea. High-density D-sub 26-pin connectors, 2 channels per connector (±SIG, ±EXC, ±SENSE, ±SHUNT, SHIELD)
Excitation:
Type: Bipolar (zero centered)
Max Output: 20 V, 30 mA w/ remote sense
Steps: Programmable from 0 to 20 V in 10 mV steps
Accuracy (Excitation ≥ 2.5 V): ±0.03%; ±200 μV after auto-cal, ±5° from Tcal
Noise: 100 μVrms, 3 Hz to 100 kHz
Drift: ±0.0025%/°C of setting or ±50 μV/°C, whichever is greater
Automatic Bridge Balance:
Type: Voltage insertion at amplifier input
Range: 51.2 mV per V of excitation
Resolution: 1 μV per V RTI, bridge output zeroed to < 1 mV per V RTO
Shunt Calibration:
Precision 100 kΩ resistor applied across ± shunt pins under program control
Kulite Support:
5th wire temperature readout of equipped 5-wire Kulite pressure sensors
Sensor Health Monitor:
Excitation Monitor: Transducer excitation voltage is measured and reported
Resistance Monitor: Transducer resistance is measured and reported
Sensor Open/Short Monitor: Transducer open or short condition is monitored and reported
Front Panel: RJ45 Ethernet connector (x1), signal grounding post (x1), power entry connector (x1), diagnostic port (x1), power switch, IRIG-B synchronization interface (3x BNCs), buffered analog output on 50-pin D connector
Rear Panel: High-density 26-pin input D-sub connectors (x8), BNC test connectors (x2)
Sensor Type:
2-wire dynamic strain, AC or DC voltage
Input Connector:
8 ea. High-density D-sub 26-pin connectors, 2 channels per connector (±SIG, SHIELD)
Excitation:
Type: 2-wire Balanced Constant Current (BCC)
Steps: Programmable 0 to ±20 mA in 100 μA steps
Compliance (linear range): 22 − (I x 700) V minimum
Input Impedance: 100 kΩ per side
Accuracy (EXC ≥ 1 mA): ±0.1% of setting, ±10μA
Drift: 30 nA + 0.0024% of setting per °C
Noise: 65 pA/√Hz at 1 kHz
Sensor Health Monitor:
Excitation Current: Measure actual transducer excitation current delivered to gage
Loop Resistance: Measure and report sensor + cable “loop” resistance
Compliance Headroom: Alerts the user if the DC bias voltage on input terminals
exceeds specifications
Leakage Resistance: Measure and report leakage resistance to ground
Sensor Open/Short Monitor: Transducer open or short condition is monitored and reported
Test Mode AC Current:
An AC current square wave, 50% duty cycle at programmed frequency, is injected into current loop to evaluate end-to-end system frequency response.
Level: 0.2% pk-pk of programmed excitation current
Frequency: 1-100 kHz in 1 kHz steps
Front Panel: RJ45 Ethernet connector (x1), signal grounding post (x1), power entry connector (x1), diagnostic port (x1), power switch, IRIG-B synchronization interface (3x BNCs), buffered analog output on 50-pin D connector
Rear Panel: High-density 26-pin input D-sub connectors (x8), BNC test connectors (x2)
SDAS Bridge Variant (SDAS16-BRG)
SDAS Dynamic Strain Variant (SDAS16-BCC)
Specifications
Front Panel: RJ45 Ethernet connector (x1), signal grounding post (x1), power entry connector (x1), diagnostic port (x1), power switch, IRIG-B synchronization interface (3x BNCs), buffered analog output on 50-pin D connector
Rear Panel: BNC input connectors (x16), BNC test connectors (x2)
Front Panel: RJ45 Ethernet connector (x1), signal grounding post (x1), power entry connector (x1), diagnostic port (x1), power switch, IRIG-B synchronization interface (3x BNCs), buffered analog output on 50-pin D connector
Rear Panel: BNC input connectors (x16), BNC test connectors (x2)
Front Panel: RJ45 Ethernet connector (x1), signal grounding post (x1), power entry connector (x1), diagnostic port (x1), power switch, IRIG-B synchronization interface (3x BNCs), buffered analog output on 50-pin D connector
Rear Panel: 50-pin D input connector (x1), BNC test connectors (x2)
Sensor Type:
Single-ended charge input for grounded or floating piezoelectric sensors
Input Connector:
Isolated female BNC connectors (16 ea.)
Maximum Input:
100,000 pC
Charge Sensitivity:
Four programmable ranges provide 0.1, 1, 10, 100, and 1000 mV/pC corresponding
to full-scale ranges of 100,000 pC, 10,000 pC, 1000 pC, 100 pC, and 10 pC
LFRO:
0.5 Hz (−3 dB)
Full-scale Charge Input:
100,000 pC f ≤ 30 kHz; 100,000 x (30 kHz/f), f ≥ 30 kHz
Nominal 1% Frequency Response:
5 Hz to 100 kHz
Minimum Sensor Shunt Resistance:
Meets nominal 1% frequency response specification at 5 Hz with shunt resistance as low as 100 kΩ
Charge Conversion Accuracy:
0.25%
Shunt Calibration Capacitor:
1,000 pF ±1% (Calibrated value stored in system non-volatile memory)
SDAS Charge Variant (SDAS16-CHG)
Specifications
SDAS IEPE Variant (SDAS16-IEPE)
SDAS Voltage Variant (SDAS16)
Sensor Type:
IEPE transducer, remote charge converter (RCC), or AC or DC voltage
Transducer Connection:
Floating or grounded (programmable)
IEPE Current:
0, 2. 4, 8, 10, 12 mA
IEPE Compliance Voltage:
26 VDC ± 5%
Sensor Bias Detector:
The sensor bias detector measures the bias level and determines if it is within user defined limits.
Sensor Type:
A/D only for preconditioned voltage inputs from any sensor
Input Type:
Differential input (± 10 Vpk)
Specifications
Environmental
Temperature:
−0°C to 60°C operating, −55°C to 125°C storage
Humidity:
95% non-condensing
CE/EX European Union Hazardous Locations, ROHS:
Safety Standards: EN 61010-1
EMC Standards: EN 61326-1
Hazardous Locations Standards: EN 60079-15
Dimensions:
19’’ rack mount, 10’’ depth, 1U w/ rack mounting ears
Weight:
5 lbs 10 oz
Power
Description:
Power is supplied to the SDAS16 from either a direct DC power source or via the optional SDAS16-ACDC-50W external AC to DC supply. A power supply mating connector is provided with each SDAS16 system.
Input:
10.8 V to 30 V
DC Power Consumption:
50 W Max (30 W for A/D only variant)
Ground:
Signal and chassis ground posts are located on the rear panel. The user can connect signal ground to chassis ground for normal, ground-referred operation. Alternatively the user can reference the SDAS16 circuitry to an external ground connected to the signal ground post.
Performance Verification and Control
Go/No-Go Tests (GNG):
Built-in Go/No-Go routines verify the excitation, DC offset, AC/DC coupling, noise, charge gain (CHG version), and the DC and AC gain of the present setup prior to a test run. Tests are initiated via the SDAS16 Desktop Client software application (Option S).
Factory Acceptance Tests (FAT):
Precision Filters’ built-in test hardware and software allow for NIST traceable calibration tests on the SDAS16 unit. The test subsystem consists of the SDAS16 configured with Option F,S and the SDAS-5-TEST third-party test instruments. For traceability, a high-performance digital multimeter (DMM) is used as a reference standard and kept in calibration by a third-party metrology test lab. Test software verifies calibration and traceability information of the DMM and then proceeds, step by step, through an extensive test routine. Every system function is exercised, and all data-critical performance characteristics are accurately measured and compared to published specifications. These calibration tests are the same rigorous measurement routines performed in the factory before shipment and serve as an excellent Factory Acceptance Test (FAT) to be used by a customer upon receipt of new equipment. The SDAS16 FAT verifies all key performance characteristics, including the following: frequency response, gain accuracy, AC coupling, noise, excitation, maximum signal level, and dynamic range.
Control:
SDAS16 control is accomplished via the Ethernet interface. All parameters of the front-end signal conditioner and the digitizer are programmable via the remote interface. An optional Windows-based Desktop Client software package (Option S) adds multi-scope displays for time history and FFTs. Options F and S are required for the execution of the GNG and FAT tests. C callable APIs are available for data and control from a desktop PC running Linux or Windows OS.
SDAS Control Software
Power (cont.)
Isolation:
60 V DC or AC continuous bank isolation, signal ground to chassis ground in isolated ground switch position.
SDAS
Precision Signal Data Acquisition Systems
Prelim. Ver.Copyright © 2024 by Precision Filters, Inc.Balanced Constant Current and BCC are trademarks of Precision Filters, Incorporated.
Precision Filters, Inc.
240 Cherry Street
Ithaca, New York 14850
Telephone:607-277-3550
E-mail:pfinfo@pfinc.com
Web Site:www.pfinc.com
On the New Frontiers of Precision
Ordering Information
BCC = Dynamic Strain Variant
BRG = Bridge Variant
CHG = Charge Variant
IEPE = IEPE Variant
(N/S) = Voltage (A/D Only) Variant
Option S = Desktop Client Software Package
Option F = Factory Acceptance Test (Requires Option S)
SDAS16-<BCC|BRG|CHG|IEPE>-<S,F>