Campbell Scientific CS420 and CS425 PDCR 1830-8388 Pressure Transducer - Manual (Page 10)

CS420-L and CS425-L Pressure Transducers
or
output mV =
(sensitivity mV) (excitation V)
( ply voltage V)
∗
sup
The value and units for the sensitivity are listed on Druck’s calibration
certificate.
If the pressure range of the sensor is exceeded, the output
voltage of the transducer could exceed the input range of the
datalogger. For CRBasic dataloggers, NAN (not a number)
indicates an overrange. For Edlog dataloggers, an overrange is
represented by a -6999 in the data file or
-9999 in the monitor mode of the PC200W, PC400, LoggerNet,
or PC208(W). If this occurs, decrease the recommended
excitation voltage by ten percent. An open connection, such as a
loose wire, can mimic an overrange condition.
NOTE
5.4 Increasing the Resolution
The following instructions on increasing resolution are not
necessary for most applications. We recommend jumping ahead
to the program examples and getting your sensor up and running.
If you need a better measurement, refer back to this section. NOTE
To increase measurement resolution, adjust the excitation provided to the
sensor so that the output is close to, but not exceeding the input range of the
datalogger. An adjustment factor for the excitation can be calculated using the
following equation:
adjustment factor =
input range mV
output mV
Example:
A CR3000 datalogger is used to measure a Druck transducer. The Druck
calibration certificate lists the following values:
pressure range: 10 psig
sensitivity: 1.1
(mV/V)/psig
If a 5000 mV (5 V) excitation is applied to the sensor, the output of the sensor
will be:
output mV = (10 psig)(1.1 (mV/V)/psig)(5 V)
= 55 mV
The input ranges for the CR3000 are: ±20, ±50, ±200, ±1000, and ±5000 mV.
The sensor output of 55 mV exceeds the ±50 mV range, but using the ±200
mV range decreases the resolution. By calculating and applying an adjustment
factor, you obtain the best measurement for your sensor.
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