Specifications
SPD series
Version 1.0
Excitation voltage
The excitation of the sensor can be AC or DC. Specifications are given
with a DC excitation of 5V. In order to avoid electrical breakdown it is
advised not to exceed the maximum values given.
Offset
The offset value is the electrical output voltage (imbalance) of the
pressure sensor when zero pressure is applied. The offset value for the
absolute type is determined by extrapolating the measured values at
two different pressures (atmospheric air and 0.05 Bar). The pressure in
reference chamber is about 25 mTorr (3.33 Pa).
Temperature coefficients
Silicon resistors are very temperature dependent. The overall drift of the
resistors is not of interest to most users (The bridge resistors are
located on the same die). The temperature coefficients of the offset and
span, however, are very important. All the temperature coefficients are
given in percentage of full-scale range (FS) and over a temperature
range of 100 °C.
The maximum value of the temperature coefficient of the span is minus
27%, which means that worst case the span becomes 27% smaller
over the full temperature range of 100 °C. The offset will vary no more
than ±7% of the span over the same temperature range.
Calculation example (please refer to the parameter table above)
Suppose the use of a pressure sensor of type SPD 015G over a
temperature range of 100 °C. The typical full scale span is 140 mV. The
offset (at a fixed temperature) will be between -50 and +50 mV.
Offset
When the static part of the offset has been nulled, the offset can still
vary ±7% of 140 mV (± 9.8 mV), over the temperature range of 100°C.
Span
The typical full-scale span is 140 mV and the typical temperature
coefficient of the span equals –22 %FS/100 °C.
Typically, you would therefore have a span, which varies between 140
mV and 109 mV (140 mV minus 22%), over the full temperature range
of 100 °C.
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