Signal Conditioning and Amplification

What are the Benefits of Signal Conditioning?

Signal Conditioning improves the performance and reliability of the measurement system. A typical signal conditioning system includes the signal conditioning hardware, which works as an interface between the raw signals and transducer outputs and the measurement device. In turn, it supplies functions such as signal amplification, attenuation, electrical isolation, filtering, powering, overload detection and Transducer Electronic Data Sheet (TEDS) support.

Brüel & Kjær provides a number of signal conditioning solutions. When determining which conditioner to use, you should consider the type of transducer as well as the conditioner's benefits to the measurement system, including the following critical features and characteristics. 

Number of Channels

For multi-channel tests, having more channels in the signal conditioner makes for a simpler system (for example, one power supply or battery for all the conditioned channels).

Channel Control

For units with adjustable settings, manual control is the easiest way to change configuration. In automated or multi-channel systems, computer control offers big time savings.

For very large systems, it is desirable to control as many channels as possible from a single PC.

Maximum and Minimum Frequency and Adjustable Filters

Besides needing to cover the measurement's frequency range, a conditioner's analogue filter can remove portions of the signal outside the range of interest. For example, in-vehicle measurements of sound often have very strong low-frequency content below 20 Hz. A 20 Hz high-pass filter will attenuate the signal below the audio range which may improve the measurement system's noise floor at mid to high frequencies.

Minimum and Maximum Gain

When using data acquisition equipment with adjustable input ranges, the noise floor of the complete measurement system (from transducer through conditioning to data acquisition) can be improved by adding gain in the conditioner.

Uni (Fine) Gain Adjustment

The sensitivity of a transducer in engineering units or volts typically varies significantly between individual transducers. Compensating for the individual sensitivities using fine gain control in the conditioner removes this error.

Transducer Electronic Data Sheet (TEDS)

Significant measurement errors can be automatically avoided when the fine gain adjustment of the conditioner is read from the transducer's built-in Transducer Electronic Data Sheets (TEDS).

Multi-unit Design

Rack mounting is a convenient way of organising laboratory- based measurement systems where all the conditioning and data acquisition can be combined into one frame. For most signal conditioners, you can order an optional 19-inch rack and/ or a multi-unit frame, with which 1 or more conditioner can be mounted.

Looking at acoustic transducers, signal conditioning presents many many useful features:

Polarization Control

The working principle of the condenser microphone is based on a fixed charge. This charge is established, either with a very stable external polarization voltage, typically 200 V, via a large resistor, or by an electret layer deposited on the microphone's backplate, in which case the external polarization voltage should be set to 0 V.

CIC

Charge Injection Calibration (CIC) is a technique for on-line verification of the integrity of the entire measurement chain, for example, microphone, preamplifier and cabling. Even microphones remote from the input stage/conditioning amplifier can be verified. The basic philosophy behind CIC is that if we have a known condition (for example, a properly calibrated microphone) and establish a reference measurement, then as long as the reference value does not change, nothing has changed, for example, the microphone calibration will still be

Filtering

Acoustic weighting curves

A-weighting Filters

Sound measurements often specify A-weighting to reflect the acuity of the human ear, which does not respond equally to all frequencies. Using analogue A-weighting filters can also have the same benefit of improving the measurement system's noise floor at mid to high frequencies for in-vehicle measurements.

For further comparisons and in-depth specifications, please see the individual conditioner's product data. For help selecting a signal conditioner, please get in touch with your local Brüel & Kjær sales representative.