b. At that measurement rate, what is the best attainable resolution for the measurements?
Resolution increases as the f
N1
decreases, but measurement time increases. Solving the
equation for f
N1
gives the following:
With a measurement time of 5 ms (5000 µs), settling time of 100 µs, and 7 repetitions, f
N1
must be greater than 13807 Hz.
Thus, to improve measurement resolution, f
N1
should be set to 15000. According to
voltage measurement range and resolution
(p. 42), this would improve the resolution to
9.012 µVRMS for the largest voltage range, ±5000 mV.
D.3 Example 3
How fast can a VOLT 116 measure ten 3 kΩ full-bridge sensors using the default settling time (500
µs) and both excitation and input reversal, and achieve a resolution of less than 1 µV
RMS
? For
easier wiring, limit the sensors excited per excitation terminal to four.
The full-bridge measurement,
BrFull()
, makes a differential measurement. It is given that the
measurement will use input reversal, so the resolution is given in the third column of
voltage measurement range and resolution
(p. 42). To achieve a resolution of less than 1 µV
RMS
within the ±5000 mV range, f
N1
must be 100 Hz or better.
The measurement time is figured separately for each excitation channel used, where the
repetitions are the number of sensors excited on that channel. In this setup, three excitation
terminals are used, X1 – X3. The measurement times are given by the following equations:
VOLT 100 series
53
