Campbell Scientific CS420 and CS425 PDCR 1830-8388 Pressure Transducer - Manual (Page 8)

CS420-L and CS425-L Pressure Transducers
The sections that immediately follow are for CRBasic, Edlog,
and Keyboard/Display users. Short Cut users can jump ahead to
the Maintenance section (page 21). NOTE
5.2 Using CRBasic, Edlog, or the Keyboard/Display
For dataloggers programmed with CRBasic use the BrFull instruction to make
a four-wire measurement and BrFull6W to make a six wired measurement.
For Edlog dataloggers use Instruction 6–Full Bridge Measurement to make a
four-wire measurement or Instruction 9–Full Bridge with Measured Excitation
to make a six-wire measurement. These instructions require a unique
multiplier and offset to be calculated for each sensor. Your datalogger manual
has a detailed explanation of these instructions and there is extensive help in
the CRBasic editor. Also see the programming examples that start on page 7
of this document.
5.2.1 Calculating the Multiplier
The value for the sensitivity is listed on each transducer’s calibration
certificate. It will be shown in units of either mV/V/psig or mV. Based on the
units of sensitivity, choose one of the following equations to calculate the
multiplier (M):
(V) Voltage y (mV)/Suppl y Sensitivit
(psig) Range
= M or
) (mV/V/psig y Sensitivit
1
= M
After calculating M, use the conversion factor listed in Table 1 to convert the
value to the desired engineering units.
TABLE 1. Conversion Factors
To change To Multiply by
mb ft of water 0.0334883
psig ft of water 2.306725
mb meters of water 0.010207
psig meters of water 0.70309
Example:
When Druck calibration certificate lists the following values for a sensor:
sensitivity = 0.98 (mV/V)/psig
The multiplier is:
M = 1/(0.98 (mV/V)/psig)
= 1.02 psig/(mV/V)
If the desired engineering units are feet of water, the multiplier becomes:
(1.02 psig/(mV/V))*(2.306725 ft of water/psig)= 2.3529 ft of water/(mV/V)
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