Statement of Work
Signal Conditioning System
1.0 Background
NASA Langley Research Center requires a replacement signal conditioning system to replace an obsolete signal conditioning system used in environmental vibration testing. The system shall be capable of simultaneous conditioning of 32 channels of mixed voltage and IEPE acceleration signals.
2.0 Acronyms
BNC - Bayonet Neill-Concelman connector
FAT - Factory Acceptance Test
GUI - Graphical User Interface
IEPE - Integrated electronic piezoelectric devices
RETMA - Radio Electronics Television Manufacturers Association
SPT - System Pretest Check
TEDS - Devices implementing IEEE 1451.4 standard for embedding Transducer Electronic Data Sheets
U - Rack Unit, 1.75 inches
3.0 Requirements
The Vendor shall provide all labor, materials, and equipment necessary to provide a signal conditioning system that meets all requirements specified herein.
3.1 General Requirements
1. The system shall be capable of simultaneous conditioning of 32 channels of mixed voltage and IEPE acceleration signals
2. A Graphical User Interface (GUI) shall be provided to furnish control over the system
3. The system shall be rack mountable in a standard 19-inch RETMA cabinet with all necessary mounting hardware and provision for cooling included
4. The system shall occupy no greater than 3U (5.25 inches) of vertical rack space
5. The system shall be modular in design so that signal conditioner cards may be inserted or removed from the system through the front of the unit without removing any cables
6. The system shall be compatible with US AC power standards of 120V at 60 Hz
7. The system shall be upgradeable in the future to accommodate signal conditioning of voltage and IEPE acceleration signals of up to 64 channels
8. The system shall have built-in temperature, power supply and cooling fan monitoring with alarms. The user shall be alerted if the temperature exceeds operating specifications, the power supply operates out of tolerance, or the cooling fans operate out of specification.
9. The system shall have a scope monitor BNC output for monitoring any channel's output with an external measurement device.
10. Input Connections: The vendor shall provide input connecting cabling and connectors to interface to existing equipment. The connection is through four 25-pin D-sub connectors. The typical pin-outs for the connectors is shown in Table 3.1. Each channel shall consist of two conductors plus a shield. Cable length shall be a minimum of 4 ft.
11. Output Connectors: The vendor shall provide input connecting cabling and connectors to interface with the inputs of a Precision Filters Model 4164 Matrix Switch. Cable length shall be a minimum of 4 ft.
 
Table 3.1 Input Connecting Cable Connection
Existing Connector Mating Connector Cable
DB25P DB25S, crimp sockets
Glenair 550T102M3R3H backshell
or equivalent 2-cond, twisted, shielded, 20-22g, jacketed, 4 ft length
or equivalent
Channel Signal Pin Number Cable
0 +Signal 1
0 -Signal 14 0
0 Shield 15
1 +Signal 2
1 -Signal 3 1
1 Shield 16
2 +Signal 5
2 -Signal 4 2
2 Shield 17
3 +Signal 6
3 -Signal 7 3
3 Shield 18
4 +Signal 20
4 -Signal 8 4
4 Shield 19
5 +Signal 10
5 -Signal 9 5
5 Shield 22
6 +Signal 11
6 -Signal 12 6
6 Shield 23
7 +Signal 24
7 -Signal 25 7
7 Shield 13
Ground 21 1-cond, 20-22g, Jacketed

3.2 Signal Conditioning Requirements
Each system channel shall be capable of providing signal conditioning to general purpose voltage type sensors and IEPE type sensors. Signal conditioning includes, as a minimum, signal gain, signal filtering, signal grounding control, and sensor supply current for IEPE type sensors.
3.2.1 General Characteristics
1. Each channel shall be compatible with IEPE TEDS type sensors and shall have an integrated TEDS reader capability. This TEDS reader will be capable of reading TEDS sensor data over cable lengths up 500 feet. TEDS information shall be reportable in text or spreadsheet form.
2. Each channel shall have a "short" test mode in order to ground the input stage so that amplifier noise and DC offset may be examined.
3. Each channel shall have a sensor bias measurement function that allows remote measurement of the attached sensor bias voltage via the software interface. The software interface will also include a mechanism to compare measured sensor bias voltage to user defined thresholds and produce warnings if the measured bias is outside the defined range.
4. Each channel shall have overload detection and out-of-tolerance bias detection with user indication in software and front panel indicator light.
5. The system shall have the following general channel specifications:
a. Amplitude Accuracy: ±0.25% 2 kHz (max) for a system gain of x1
b. Amplitude Match: ±0.5 %
c. Phase Match: ±3° (max)
3.2.2 Input Characteristics
The input stage of each channel shall be balanced differential and have the following minimum specifications:
1. Input Protection: ±30 V
2. Input Impedance: 1 MΩ, 100 pF per side (IEPE current source disconnected)
100 kΩ, 100 pF per side (IEPE current source connected)
3. Maximum Signal Level: ±10 Vpk
4. Common Mode Rejection Ratio: -80 dB min, 5Hz to 2 kHz for a system gain of x1
5. Each system channel shall have an IEPE current source capable of supplying current to IEPE type sensors with and without TEDS capability as well as remote charge converters with the following minimum specifications:
a. Programmable supply current of 0, 2, 4, and 8mA; ±5% accuracy
b. The IEPE supply shall have IEPE compliance voltage range of: -5VDC to 26VDC
c. Programmable input mode selection of isolated or grounded to accommodate floating or grounded sensor connections
d. The input shall have an AC low frequency roll-off filter to reject the IEPE supply voltage
3.2.3 Amplifier Characteristics
Each system channel shall have a software programmable amplifier stage. The amplifier shall have the following specifications, as a minimum:
1. The amplifier shall provide protection from large out-of-band energy or transients that could cause clipping prior to filtering
2. Gain: x1, x10, and 100x
3.2.4 Filter Characteristics
Each system channel shall have a software programmable low-pass filter stage. The low-pass filter shall have the following characteristics, as a minimum:
1. Type: 4-pole, time delay, linear phase response low-pass filter
2. Cutoff Frequencies:
a. One low frequency ~500 Hz
b. Two midrange frequencies ~2 kHz, and ~5 kHz
c. One high frequency ~10 kHz
3. A wideband (filter bypass) mode of operation shall be supported. In wideband mode, the filter shall be bypassed but the amplifier shall be fully operational.
4. Cutoff Amplitude: -5%
5. Stop-Band Attenuation: 80 dB
6. Phase Distortion at Cutoff Frequency: 0.0 deg
3.2.5 Output Characteristics
Each system channel shall be equipped with two isolated output stages with the following specifications:
1. Type: Single-ended output.
2. Impedance: 10 Ω, 100pF
3. Max Output: ±10 Vpk
4. Noise: 100 µVrms filters bypassed, referenced to output
3.3 System Control Requirements
1. System control shall be via a Graphical User Interface (GUI) running on a PC computer utilizing a Window 7/10 operating system. (The control computer shall be furnished by the Government).
2. System control shall include, as a minimum:
a. System diagnostic testing
b. System set-up (channel type, gain, IEPE sensor bias, and filter cut-off frequency)
c. System monitoring
d. Channel monitoring (cable connection - open/short, transducer health, sensor overloads, and IEPE sensor bias)
e. System calibration
3. The GUI shall allow for customizing display panels and control groups to the users' preference.
4. The GUI shall support storage of system setups for later retrieval.
3.4 System Calibration
The signal conditioner shall provide a built-in test capability. Two levels of test shall be provided: a Factory Acceptance Test (FAT) and a System Pretest Check (SPC).
3.4.1 General Characteristics
1. The FAT and SPC tests shall be run "in place" without removing signal cards from the system. All required test cables and adapters for conducting the tests shall be included with the system hardware.
2. The system shall be capable of generating text or pdf documentation documenting the results of the system calibration.
3. The FAT test shall be NIST traceable.
4. The FAT and SPC tests shall be controlled via a Graphical User interface.
5. A list of equipment used to perform the tests (model #, serial # and calibration due date) shall be included in the test report.
3.4.2 Factory Acceptance Test Characteristics
The system shall include an automated FAT feature that provides for NIST traceable periodic calibration. The FAT feature shall include all test required to certify a NIST traceable calibration of the unit.
3.4.3 System Pretest Check
The system shall provide a self-check capability that checks the health of the before the start of data acquisition. This feature shall include:
1. Failed channel
2. Common mode rejection
3. Gain accuracy
4. Filter cutoff accuracy
5. IEPE current levels

Bid Protests Not Available