Precision 28000 Solutions for Measuring Bridge, Strain, Temperature, Vibration and More

Precision Filters, Inc. (PFI) offers a complete line of conditioners to measure static and dynamic strain (including high temperature strain), RTDs, thermocouples, IEPE sensors or any bridge-type transducer including pressure sensors, piezo-resistive accelerometers, load cells and more. We offer models with an analog bandwidth greater than 1 MHz and programmable filter selections between 1 Hz and 200 kHz. Choose from our line-up of four or eight channel cards with performance to match your requirements.

All of PFI’s Bridge conditioners have built-in test hardware that makes automated system verification and validation easy. The test bus enables automated calibration signal insertion at the amplifier input. Any output channel may be observed without disrupting the normal output using the monitor bus. Our four channel cards have real time monitoring of excitation, transducer loop resistance, sensor leakage to ground and more. Never before has a system provided you with so much pre-test confidence that your system is functioning properly.

Measurements

  • Dynamic Strain Gage
  • Static Strain Gage
  • Full Bridge and Other Bridge Configurations
  • Piezo-resistive Pressure Sensors (Kulite)
  • Piezo-resistive Accelerometer
  • IEPE Sensors
  • Resistance Temperature Detectors (RTD)
  • Load Cell Sensors
  • MEMS Transducers
  • Hot Wire Anemometry
  • AC or DC Filter/Amplifier

Spec Sheets and Technical Docs

Innovative Performance Technologies

Sensor Health Monitoring

At Precision Filters, we know that even the best signal conditioner is of little value if the sensor or input wiring is faulty. A failed sensor or cable discovered after the test is too late...

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At Precision Filters, we know that even the best signal conditioner is of little value if the sensor or input wiring is faulty. A failed sensor or cable discovered after the test is too late and will result in lost data that can never be recovered. Quick and easy visibility of cable and sensor health allows timely corrective actions to save crucial data. Test hardware and software in our bridge conditioner products automate sensor and cable health checks. Transducer excitation, resistance and even leakage to ground are reported in real time.

Balanced Constant Current

Precision Filters’ proprietary Balanced Constant Current (BCC™) excitation is optimized for making dynamic and static strain measurements on single active strain gages and RTD’s..

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Precision Filters’ proprietary Balanced Constant Current (BCC™) excitation is optimized for making dynamic and static strain measurements on single active strain gages and RTD’s. Use 2-wire BCC to make accurate dynamic measurements on a single active strain gage or 4-wire BCC for static and dynamic strain or RTD measurements.

BCC excitation provides a true balanced input for rejection of common-mode signals. Electrostatic pickup is reduced when compared to single-ended constant current excitation or a quarter-bridge configuration with remote completion resistors or unbalanced current sources. The balanced current excitation circuit operates properly even under certain common gage fault conditions such as a direct short of the gage to the test model.

Measuring Resonant Transducers

Some transducers such as piezo-resistive pressure transducers can have very high resonant frequencies that can be excited by transient events and this...

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Some transducers such as piezo-resistive pressure transducers can have very high resonant frequencies that can be excited by transient events and this out-band signal can be larger than the signal of interest.

The 28000 amplifier gain is distributed as “pre-filter” and “post-filter” gain to allow the filter to remove out-band signals such as transducer resonance while still achieving the required full-scale in-band signal level. Using the 28000 “reserve” feature, the user can specify the required protection against out-band noise and the pre- and post-filter gain are automatically distributed to provide this protection. The pre-filter gain is set to achieve the required amplifier headroom for the out-band signals prior to the filter while maximizing dynamic range. After the filter removes the out-band signals, the post-filter gain is set to achieve the desired full-scale output. The 28144 card may be equipped with either a low-pass filter or a high-pass filter cascaded with a low-pass filter to form a band-pass filter. The band-pass configuration and the distributed amplifier gain provide the user ultimate flexibility to eliminate sources of either high frequency or low frequency noise.

Frequency or Time Domain Measurements

The Precision Filters’ FLAT/PULSE filter technology allows the user to set the frequency response characteristics of the signal conditioner under program control...

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The Precision Filters’ FLAT/PULSE filter technology allows the user to set the frequency response characteristics of the signal conditioner under program control. For transient tests or tests where time-domain wave shape preservation is important, program the filter characteristic to PULSE mode. The PULSE mode provides linear phase response, which is required for time-domain wave shape reproduction and outstanding transient response with low overshoot and ringing. For frequency domain analysis, selecting the FLAT filter characteristic will result in outstanding transfer function flatness and a sharp, selective filter response. FLAT/PULSE filter technology is available on all Precision Filters’ strain and bridge conditioners.

Components and Features

Dual Mode Constant Voltage & BCC Excitation

Precision’s line-up of quad-channel conditioners provides the versatility to condition a wide variety of constant-voltage excited sensors including full bridges and sensors that require precise bridge completion. Use BCC excitation technology for 2- or 4-wire strain gage or RTD measurements. Choose the full-featured high performance 28144 card, the 28124 card for multiple filtered/wideband outputs, the 28154 for 350 Vcm capability or the economical 28114.

Dual Mode Constant Voltage & BCC Excitation Conditioners Common Features:

  • 4 channels/card, 64 channels/system
  • Balanced programmable constant current or constant voltage excitation w/automatic bridge balance/transducer zero suppress
  • On-the-fly report of measured transducer excitation, resistance, open/short and leakage to ground
  • Programmable AC/DC input coupling
  • Option HC10 – RTD/Bridge/Thermocouple Configuration. 2-Wire/4-Wire 0 to 1 mA RTD excitation. RTD substitution (5 resistors), 3-step bipolar resistive shunt calibration.
  • Option HC14 – Bridge/Strain/IEPE Configuration. Prog. bridge configuration (1, 2, 4-Arm) or 2-Wire/4-Wire constant current. Programmable completion (120, 350 and 1 kOhm). Precision 255-step bipolar resistive shunt cal. IEPE input mode (8 mA constant current source).

28144 4-Channel Wideband Transducer Conditioner

  • Choice of 4- or 8-pole FLAT/PULSE low-pass filters or 8-pole band-pass filters
  • Over 2,000 unique cutoff frequency settings from 1 Hz to 204.6 kHz
  • Low noise, high CMRR amplification from x1/16 to x8192 with 0.05% resolution
  • REZCOMP™ technology to extend frequency response of accelerometer, unsteady pressure and microphone sensor measurements
  • Optional unity gain buffer for Kulite sensors equipped with 5th-wire
View the 28144 Spec Sheet

28154 4-Channel 300 Vcm Wideband Transducer Conditioner

  • 4-pole FLAT/PULSE low-pass filters
  • Over 2,000 unique cutoff frequency settings from 1 Hz to 102.3 kHz
  • Per channel isolation - 350 V channel to channel and channel to earth ground
  • Traceable per channel programmable DC voltage substitution
  • Low noise, high CMRR amplification from x1/16 to x8192 with 0.0125% resolution
  • Three wideband or filtered outputs per channel with optional isolated output
View the 28154 Spec Sheet

28124 4-Channel Wideband Transducer Conditioner

  • 4-pole FLAT/PULSE low-pass filters
  • Over 2,000 unique cutoff frequency settings from 1 Hz to 102.3 kHz
  • Low noise, high CMRR amplification from x1/16 to x8192 with 0.05% resolution
  • AC Shunt Calibration for frequency response evaluation of bridge-based sensors
  • Three wideband or filtered outputs per channel
View the 28124 Spec Sheet

28114 4-Channel Transducer Conditioner

  • 4-pole FLAT/PULSE low-pass filters
  • Five programmable cutoffs to 100 kHz
  • Amplification from x1/16 to x1024 with 0.05% resolution
View the 28114 Spec Sheet

Bridge Conditioners with Voltage Excitation

Where applications call for high performance bridge conditioning with high channel counts, the 28108 and 28118 octal filter/amplifiers with constant voltage excitation deliver low-noise and DC stability for either AC or DC bridge-based sensors or low-level voltage measurements.

Bridge Conditioners with Voltage Excitation Common Features:

  • 8 channels/card, 128 channels/system
  • Balanced programmable constant voltage excitation
  • 6-wire + shield transducer interface
  • Automatic bridge balance
  • Transducer suppress up to 10V of DC bias
  • 4-pole FLAT/PULSE low-pass filters w/filter bypass
  • Test Modes: Test-bus, Short, Zero-Excitation, Excitation Monitor

28108 4-Channel Bridge Conditioner

  • 255 programmable cutoff frequency settings
  • 25 kHz filtered or 100 kHz “wideband” bandwidth
  • Low noise, high CMRR amplification from x1/16 to x8192 with 0.05% resolution
View the 28108 Spec Sheet

28118 4-Channel Bridge Conditioner

  • 5 programmable cutoff frequency settings from 100 Hz to 30 kHz
  • 30 kHz filtered or 190 kHz “wideband” bandwidth
  • Programmable amplification from x1/16 to x1,024 with 0.05% resolution
View the 28118 Spec Sheet

Dynamic Strain with Current Excitation

Measurements of dynamic strain with PFI’s balanced constant current technology are much less susceptible to the noise pickup and lead resistance desensitization that plague single-ended constant current topologies.

28458 Dynamic Strain Conditioners Features:

  • 8 channels/card, 128 channels/system
  • Balanced programmable constant current excitation with 20 V compliance
  • 2-wire + shield transducer interface
  • 4-pole FLAT/PULSE low-pass filters w/filter bypass
  • 5 programmable cutoff frequency settings
  • 100 kHz filtered or 190 kHz “wideband” bandwidth
  • Programmable amplification from x1/16 to x1024 with 0.05% resolution
  • On-the-fly report of measured transducer excitation resistance and leakage to ground
  • Sensor open and short detection
  • Test Modes: Test-bus, Short, Zero-Excitation
View the 28458 Spec Sheet
  

 

 

Bridge and Strain Conditioner Card Selection Guide

Card28144281142812428124-EA28154281082811828458
TypeAC/DC Voltage with Const. Voltage and Current ExcitationAC/DC Voltage with Const. Voltage and Current ExcitationAC/DC Voltage with Const. Voltage and Current ExcitationEnhanced Accuracy AC/DC Voltage with Const. Voltage and Current ExcitationHigh Common Mode AC/DC Voltage with Const. Voltage and Current ExcitationAC/DC Voltage with Const. Voltage ExcitationAC/DC Voltage with Const. Voltage ExcitationAC/DC Voltage with Const. Voltage Excitation
Common Mode Voltage Range10 V10 V10 V10 V350 V10 V10 V10 V
Channels/ Card44444888
Applicable TransducerStatic or dynamic strain w/ BCC™, pressure, RTD, load, accel., AC/DC filter/amp, any bridge-type sensorStatic or dynamic strain w/ BCC™, pressure, RTD, load, accel., AC/DC filter/amp, any bridge-type sensorStatic or dynamic strain w/ BCC™, pressure, RTD, load, accel., AC/DC filter/amp, any bridge-type sensorStatic or dynamic strain w/ BCC™, pressure, RTD, load, accel., AC/DC filter/amp, any bridge-type sensorStatic or dynamic strain w/ BCC™, pressure, RTD, load, accel., AC/DC filter/amp, any bridge-type sensorStrain, pressure, RTD, load, accel., AC/DC filter/amp, any full bridge-type sensorStrain, pressure, RTD, load, accel., AC/DC filter/amp, any full bridge-type sensorDynamic strain, w/ BCC™, AC filter/amp
Interface

2-10 Wire Constant Voltage w/ Programmable Bridge Completion, Shunt Calibration

2/4 Wire Constant Current

2-10 Wire Constant Voltage w/ Programmable Bridge Completion, Shunt Calibration

2/4 Wire Constant Current

2-10 Wire Constant Voltage w/ Programmable Bridge Completion, Shunt Calibration

2/4 Wire Constant
Current

2-10 Wire Constant Voltage w/ Programmable Bridge Completion, Shunt Calibration

2/4 Wire Constant
Current

2-10 Wire Constant Voltage w/ Programmable Bridge Completion, Shunt Calibration

2/4 Wire Constant
Current

2 to 6 wire w/ Shield2 to 6 wire w/ Shield2 wire w/ Shield
ExcitationConstant Voltage:
0 to 20.475 V;

 

BCC: 0 to 20.475 mA

Constant Voltage:
0 to 20.475 V;

 

BCC: 0 to 20.475 mA

Constant Voltage:
0 to 20.475 V;

 

BCC: 0 to 20.475 mA

Constant Voltage:
0 to 20.475 V;

 

BCC: 0 to 20.475 mA

Constant Voltage:
0 to 20.475 V

 

BCC: 0 to 20.475 mA

Constant Voltage:      0 to 20.475 VConstant Voltage:      0 to 20.475 VBCC:        0,5,10,15,20 mA
Bandwidth>1.5 MHz
(Opt. W)
190 kHz250 kHz250 kHz250 kHz100 kHz190 kHz190 kHz
Gainx1/16 to x8192 w/ 0.05% Resolutionx1/16 to x1024 w/ 0.05% Resolutionx1/16 to x8192 w/ 0.0125% Resolutionx1/16 to x8192 w/ 0.003% Resolutionx1/16 to x8192 w/ 0.025% Resolutionx1/16 to x8192 w/ 0.05% Resolutionx1/16 to x1024 w/ 0.05% Resolutionx1/16 to x1024 w/ 0.05% Resolution
Filter4-Pole Flat/Pulse Low-Pass w/ optional REZCOMP, 8-Pole Low-Pass or 8-Pole Band-Pass4-pole Flat/Pulse
Low-Pass
4-pole Flat/Pulse
Low-Pass
8-pole Flat/Pulse
Low-Pass
4-pole Flat/Pulse
Low-Pass
4-Pole Flat/Pulse
Low-Pass
4-Pole Flat/Pulse
Low-Pass
4-Pole Flat/Pulse
Low-Pass
Cutoff FrequenciesFlat:
2 Hz to 204.6 kHz

 

Pulse:
1 Hz to 102.3 kHz

FX02:
300 Hz, 1 kHz, 3 kHz, 10 kHz, 30 kHz

 

FX03:
10 kHz, 20 kHz, 40 kHz, 80 kHz, 100 kHz

Flat:
2 Hz to 100 kHz

 

Pulse:
1 Hz to 100 kHz

Flat:
2 Hz to 51 kHz

 

Pulse:
1 Hz to 25.5 kHz

2 Hz to 100 kHzFlat:
100 Hz to 25.5 kHz

 

Pulse:
50 Hz to 12.75 kHz

FX02:
300 Hz, 1 kHz, 3 kHz, 10 kHz, 30 kHz

 

FX03:
10 kHz, 20 kHz, 40 kHz, 80 kHz, 100 kHz

FX02:
300 Hz, 1 kHz, 3 kHz, 10 kHz, 30 kHz

 

FX03:
10 kHz, 20 kHz, 40 kHz, 80 kHz, 100 kHz

OutputsSingle-ended (SE) with Ground SenseSingle-ended (SE) with Ground Sense(3) Buffered Prog. WB/Filtered SE Outputs per channel w/ Ground Sense(3) Buffered Prog. WB/Filtered SE Outputs per channel w/ Ground Sense

(3) Buffered Prog WB/Filtered SE Outputs

Optional isolated output
(Option O)

Single-ended (SE) or Differential Output (Option T)Single-ended (SE) or Differential Output (Option T)(2) Buffered SE Outputs per Channel
Signal Conditioning Verification logo

Verification at Test Time

Continual setup, tear down and reconfiguring of sensitive test equipment demands a rigorous protocol to prove that every channel is operating correctly at test time. The 28000 System provides a layer of built-in verification and validation capability to confirm proper operation of the measurement system including sensor and cable. Upon completion of the verification testing, a status report is provided as a defendable means to document system validity at the time of the actual test.

Yearly Calibration

All test systems require periodic calibration. The Precision 28000’s automated built-in test capabilities allow the user to perform convenient, affordable NIST traceable yearly calibration tests on-site without removing the system from the equipment rack. This eliminates the need for expensive off-site calibrations and system downtime.

Learn more about 28000 NIST Traceable Testing >