Analog sensor signal conditioners have specific features that offer
capabilities that cannot be filled by a microprocessor signal conditioner.
Microprocessor based sensor signal conditioners have a number of basic limitations, when
compared to analog sensor signal conditioners. Speed and resolution are the two, most important differences.
Microprocessor based sensor signal conditioners use digital conversion as the center of the design. Analog to digital or A-D conversion, software calculation, and digital to analog or D-A conversion is the basic method. Both A-D and D-A conversion have limited
converter resolution. The converter resolution may be as little as: 8 bit, 128 step, or 1%. Additionally; both A-D and D-A conversion have limited
converter update rates. The converter update rate may be as little as: 1 update per second. These limitations impact the sensor signal conditioners ability to report, finer temperature changes than the resolution or more rapid changes than the update rate.
Analog based sensor signal
conditioners use instrumentation amplifiers as the center of the design.
Specifically designed signal gain ranges are designed into the circuit
with a specific use in mind. Amplifiers do not have a resolution
associated with them. Amplifiers are often said to have infinite
resolution. The main limit to amplifier signal readability is the signal
to noise ratio. As a signal increase becomes infinitely small, it may be
overwhelmed by background noise. This is generally much smaller that the
resolution of an a-d (which has it's own noise issues, in addition to it's
resolution issues). Additionally; analog conditioning does not use an
update period associated with it. The response limit of an amplifier is an
issue of the bandwidth of the amplifier and any filtering circuitry. As
amplifiers typically offer bandwidths of hundreds of KHz or higher, is is
possible to see sensor transient response measurement in mS periods or
smaller.
Where is this important? When you need
fine resolution, fast response, or both. How the use of an A-D based signal
conditioner impacts your measurement is in the step response to changes of
sensed value it can create in your measurement data. There are 2 types of
step that you can see, the step of the A-D precision and the step of the
delay in updates while your signal is increasing or decreasing in value.
The ROI-XMA is an improved
way to read sensors. Multiple sensor types. Multiple signal ranges. High
linearity. High precision. Fast response. Long transmission distances.
True analog signal conditioning, not microprocessor based A-D conversion.
