User guide

Veloce 50 Operating Manual

6.3 RELATIVE VERSUS ABSOLUTE MEASUREMENTS

All of Fiso' FTI, UMI, DMI and BUS series of fiber-optic conditioner are absolute measurement

conditioners as opposed to relative measurement conditioners. However the Veloce series of conditioners

offered by Fiso Technologies are relative measurement conditioner. The differences between these two

types of conditioner are explained in the next paragraphs.

6.4 ABSOLUTE MEASUREMENT CONDITIONER

Absolute measurement means that the data readings — which are the results from the conditioning of the

sampled signal of the transducer — are absolute or true measurement values of the physical stimulus

(strain, pressure, etc.). One important consequence of using absolute measurement conditioner is that

there is no loss of the true reference (or initial state) of the transducers when the conditioner is turned OFF

or reset.

6.5 RELATIVE MEASUREMENT CONDITIONER

Relative measurement means that the data readings — which are the results from the conditioning of the

sampled signal of the transducer — are measurement values relative to an initial or reference value of the

physical stimulus. One important consequence of using relative measurement conditioner is that it is not

possible to recover the true reference or initial value of the transducers when the conditioner is turned ON

or is reset. Because the initial value of the transducer is not known, a common practice is to set the output

of the conditioner to zero each time it is turned OFF or is reset.

Figure 5 shows the basic consequence of using a relative measurement conditioner. The first graph of the

figure is the absolute or true strain values versus time as it would be measured using an absolute

measurement conditioner. The graph of example 1 shows the measured strain values using a relative

measurement conditioner started at an initial time

(i.e. t

is the time at which the conditioner is tuned ON

or is reset) The graph of example 2 is same as example 1 except that the measurements are started at a

different initial time

. In both cases the measured strain values are relative to the initial value of the

transducer at time

but because the initial state of the transducer is different at these two times, the

relative strain value differs too.