28000 Voltage Filter/Amplifier Overview

Precision 28000 Solutions for Amplifying Low-Level Voltage Input Signals

Measurements

  • Anti-Aliasing Filters with Programmable Amplifiers
  • General Purpose Voltage Amplifier for Dynamic Measurements
  • Low-Drift DC Amplifier for Low-Level DC Signals
  • Underwater Acoustics
  • Pyroshock Measurements
  • Wind Tunnels

8-Channel 200 kHz Filter/Amplifiers

The 28608B and 28618 Octal Programmable Filter/Amplifier cards are ideal for conditioning low-level voltage inputs in front of high-resolution digital data acquisition systems. The cards feature balanced differential inputs and distributed programmable gain with fine resolution for engineering units scaling. Filter cutoff and characteristics are programmable to match the requirements of the particular measurement. Choose FLAT mode for optimal frequency domain performance or PULSE mode for critical time domain measurements. The filters may be bypassed under program control for wideband measurements.

 

2-Channel 3 MHz Filter/Amplifier

The 28612 Dual-Channel 3 MHz Programmable Filter/Amplifier provides two channels of low noise amplification and 6 pole low-pass filters with programmable cutoff frequencies from 5 kHz to 3.15 MHz. The 28612 input stage can be programmed to receive single ended or differential signals and the input may be programmed for Hi-Z or 50-ohm termination. The Dual mode “FLAT/PULSE” filter has programmable characteristics that may be optimized for either time or frequency domain measurements.

Innovative Performance Technologies

Balanced Differential Input Topology

The 28608B and the 28618 input stage is a high impedance balanced differential input topology that may be used to receive differential signals from a bridge type transducer or to condition grounded (single-ended) voltage sources without introducing ground loops...

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The 28608B and the 28618 input stage is a high impedance balanced differential input topology that may be used to receive differential signals from a bridge type transducer or to condition grounded (single-ended) voltage sources without introducing ground loops. The input is versatile in that it has low DC drift for DC measurement applications, low noise for wideband AC measurements and is equipped with programmable AC/DC coupling. AC coupling is useful for eliminating large DC bias on the signal so that more channel gain can be applied in order to emphasize small AC fluctuations in the signal.

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 out-band signal can be larger than the signal of interest. Sources of unwanted low frequency noise can exist such as engine sub-harmonics, triboelectric noise from cable whip or pyro-electric noise from the sensor caused by the large temperature gradients...

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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. Sources of unwanted low frequency noise can exist such as engine sub-harmonics, triboelectric noise from cable whip or pyro-electric noise from the sensor caused by the large temperature gradients.

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.

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. 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...

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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’ Voltage Filter/Amplifier Products.

Precision 28000 Voltage Filter/Amplifier Features

Dual Mode Charge and IEPE Conditioners Common Features:

  • Balanced differential inputs with programmable AC/DC coupling
  • Input MUTE mode to terminate unused channels in safe, quiet state
  • Pre-filter overload detection
  • Precise digital calibration
  • Single-ended outputs with ground sense
  • Programmable test modes for calibration signal injection and input short, allowing for automated measurement system validation
  • Output monitor bus
  • Auxiliary front-panel output connection supports the use of Precision Filters’ output buffer modules for adding up to two buffered outputs per channel

28608B 8-Channel Programmable Filter/Amplifier Features:

  • Zero Suppress
  • Distributed gain of x1/16 to x8192 with 0.05% resolution
  • 4 or 8-pole low-pass filters or 8-pole band-pass filters with programmable flat/pulse characteristics
  • Cutoff frequencies: Pulse Mode: 1 Hz to 102.3 kHz Flat Mode: 2 Hz to 204.6 kHz
  • Programmable wideband (500 kHz) or filtered operation
View the 28608B Spec Sheet

28618 8-Channel Programmable Filter/Amplifier Features:

  • Distributed gain of x1/16 to x1024 with 0.05% resolution
  • 4-pole low-pass filters with programmable flat/pulse characteristics for optimized time domain or frequency domain performance
  • Cutoff frequencies: 300, 1k, 3k, 10k, 30 kHz and wideband (190 kHz)
View the 28618 Spec Sheet

 

  • Two channels per card, 32 channels per chassis
  • Programmable single-ended/differential input
  • Programmable AC/DC input coupling
  • Programmable input termination (50 Ohms or Hi-Z)
  • Programmable gain: x1, 2, 5, 10, 20, 50, 100, 200, 500, 1000
  • Six-pole low-pass filters with programmable flat/pulse characteristics
  • Cutoff frequencies programmable from 5 kHz to 3.15 MHz
  • Precise digital calibration
View the 28612 Specification Sheet >

Voltage Filter/Amplifier Selection Chart

Card28608B2861828612
TypeAC/DC VoltageAC/DC VoltageAC/DC Voltage
Channels/Card882
Applicable TransducerLow-Level AC or DC amps and LP, HP or BP filteringLow-Level AC or DC amps and LP, HP or BP filteringLow-Level AC or DC amps and LP, HP or BP filtering
Interface2-wire with shield2-wire with shield2-wire with shield
Bandwidth500 kHz190 kHz3.15 MHz
Gainx1/16 to x8192 with 0.05% resolutionx1/16 to x1024 with 0.05% resolutionx1, x2, x5, x10, x20, x50, x100, x200, x500, x1000
Filter4- or 8-poles;  flat/pulse
low-pass or band-pass
4-pole flat/pulse low-pass6-pole flat/pulse low-pass
Cut Off FrequenciesFlat:
2 Hz to 204.6 kHz

Pulse:
1 Hz to 102.3 kHz

FX02: 300 Hz, 1 kHz, 3 kHz, 10 kHz, 30 kHz5 Hz to 3.15 MHz
OutputsSingle-ended with Ground SenseSingle-ended with Ground SenseSingle-ended
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 >